fix: Use Markdown instead of HTML markup for H3 & H4 headings (EbookFoundation#6689)

* fix: Markdown markup for `C++` heading

* fix: Markdown markup for `Дизайн и Aрхитектура` heading

* fix: Markdown H4 markup for `Next.js` heading

* fix: Markdown H3 markup for `C#` heading

Author: davorpa

books/free-programming-books-ar.md

@@ -2,7 +2,7 @@
 
 * [Arduino](#arduino)
 * [Artificial Intelligence](#artificial-intelligence)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [HTML/CSS](#htmlcss)
 * [Introduction to Programming in Arabic](#introduction-to-programming-in-arabic)
 * [JavaScript](#javascript)
@@ -34,7 +34,7 @@
 * [مدخل إلى الذكاء الاصطناعي وتعلم الآلة](https://academy.hsoub.com/files/17-%D9%85%D8%AF%D8%AE%D9%84-%D8%A5%D9%84%D9%89-%D8%A7%D9%84%D8%B0%D9%83%D8%A7%D8%A1-%D8%A7%D9%84%D8%A7%D8%B5%D8%B7%D9%86%D8%A7%D8%B9%D9%8A-%D9%88%D8%AA%D8%B9%D9%84%D9%85-%D8%A7%D9%84%D8%A2%D9%84%D8%A9/) - Mohamed Lahlah (PDF)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [سبيلك المختصر لتعلم لغة c# - برمجة الواجهات](https://www.mobarmijoun.com/2014/04/c_19.html) - Khaled Al-Saadani (Arab Coders Academy) (PDF)
 

books/free-programming-books-bg.md

@@ -1,7 +1,7 @@
 ### Index
 
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Java](#java)
 * [JavaScript](#javascript)
@@ -16,14 +16,14 @@
 * [ANSI C - Пълен справочник](https://progstarter.com/index.php?option=com_content&view=article&id=9&Itemid=122&lang=bg) - Димо Петков
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Основи на програмирането със C#](https://csharp-book.softuni.bg) - Светлин Наков и колектив
 * [Принципи на програмирането със C#](https://introprogramming.info/intro-csharp-book) - Светлин Наков, Веселин Колев и колектив
 * [Програмиране за .NET Framework](https://www.devbg.org/dotnetbook) - Светлин Наков и колектив
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Основи на програмирането със C++](https://cpp-book.softuni.bg) - Светлин Наков и колектив
 

books/free-programming-books-cs.md

@@ -1,7 +1,7 @@
 ### Index
 
 * [Bash](#bash)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Git](#git)
 * [HTML](#html)
@@ -32,13 +32,13 @@
 * [Bash očima Bohdana Milara](http://i.iinfo.cz/files/root/k/bash_ocima_bohdana_milara.pdf) (PDF)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Programovací jazyk C#](http://www.cs.vsb.cz/behalek/vyuka/pcsharp/text.pdf) - Marek Běhálek (PDF)
 * [Systémové programování v jazyce C#](https://phoenix.inf.upol.cz/esf/ucebni/sysprog.pdf) (PDF)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Moderní programování objektových aplikací v C++](https://akela.mendelu.cz/~xvencal2/CPP/opora.pdf) (PDF)
 * [Objektové programování v C++](http://media1.jex.cz/files/media1:49e6b94e79262.pdf.upl/07.%20Objektov%C3%A9%20programov%C3%A1n%C3%AD%20v%20C%2B%2B.pdf) (PDF)

books/free-programming-books-de.md

@@ -5,7 +5,7 @@
 * [Android](#android)
 * [Assembly Language](#assembly-language)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Component Pascal](#component-pascal)
 * [Git](#git)
@@ -67,13 +67,13 @@ Dirk Loser, Clemens Tamme, Philipp Schweinzer (PDF)
 * [Softwareentwicklung in C](https://web.archive.org/web/20190214185910/http://www.asc.tuwien.ac.at/~eprog/download/schmaranz.pdf) - Klaus Schmaranz (PDF)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Programmieren in C#: Einführung](http://www.highscore.de/csharp/einfuehrung)
 * [Visual C# 2012](http://openbook.rheinwerk-verlag.de/visual_csharp_2012) - Andreas Kühnel (Online)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Die Boost C++ Bibliotheken](http://dieboostcppbibliotheken.de) - Boris Schäling (Online)
 * [Lean Testing für C++-Programmierer (2018)](https://www.assets.dpunkt.de/openbooks/Openbook_Lean_Testing.pdf) - Andreas Spillner, Ulrich Breymann (PDF)

books/free-programming-books-dk.md

@@ -1,7 +1,7 @@
 ### Index
 
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Java](#java)
 * [Pascal](#pascal)
@@ -12,12 +12,12 @@
 * [Programmering i C](http://people.cs.aau.dk/~normark/c-prog-06/pdf/all.pdf) - Kurt Nørmark (PDF)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Object-oriented Programming in C#](http://people.cs.aau.dk/~normark/oop-csharp/pdf/all.pdf) - Kurt Nørmark (PDF)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Notes about C++](http://people.cs.aau.dk/~normark/ap/index.html) - Kurt Nørmark (HTML)
 

books/free-programming-books-el.md

@@ -14,7 +14,7 @@
 * [Διαδικαστικός προγραμματισμός](https://repository.kallipos.gr/bitstream/11419/1346/1/00_master%20document_KOY.pdf) - Μαστοροκώστας Πάρις (PDF)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Εισαγωγή στη C++](http://www.ebooks4greeks.gr/2011.Download_free-ebooks/Pliroforikis/glossa_programmatismoy_C++__eBooks4Greeks.gr.pdf) (PDF)
 * [Προγραμματισμός με τη γλώσσα C++](https://repository.kallipos.gr/bitstream/11419/6443/1/00_master_document-KOY.pdf) - Θεόδωρος Αλεβίζος (PDF)
@@ -49,5 +49,3 @@
 ### SQL
 
 * [Εισαγωγή στην SQL: Εργαστηριακές Ασκήσεις σε MySQL5.7](https://www.ebooks4greeks.gr/eisagwgh-sthn-sql-ergasthriakes-askhseis-se-mysql5-7)
-
-

books/free-programming-books-et.md

@@ -1,7 +1,7 @@
 ### Index
 
 * [C](#c)
-* [C Sharp](#c-sharp)
+* [C#](#csharp)
 * [Java](#java)
 * [JavaScript](#javascript)
     * [AngularJS](#angularjs)
@@ -18,7 +18,7 @@
 * [Programmeerimiskeel C](https://et.wikibooks.org/wiki/Programmeerimiskeel_C) - Wikiõpikud
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Microsoft Visual Studio Code ja C#](https://digiarhiiv.ut.ee/Ained/Doc/VFailid/CSharp_ja_VS.pdf) - Kalle Remm (PDF)
 

books/free-programming-books-fi.md

@@ -1,7 +1,7 @@
 ### Index
 
 * [C](#c)
-* [C Sharp](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [JavaScript](#javascript)
 * [MySQL](#mysql)
@@ -29,12 +29,12 @@
 * [Ohjelmoinnin perusteet ja C-kieli](http://cs.stadia.fi/~silas/ohjelmointi/c_opas) - Simo Silander
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Ohjelmointi 1: C#](https://jyx.jyu.fi/bitstream/handle/123456789/47417/978-951-39-4859-7.pdf) - Martti Hyvönen, Vesa Lappalainen, Antti-Jussi Lakanen (PDF)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [C++](https://fi.wikibooks.org/wiki/C%2B%2B) - Wikikirjasto
 * [C++-ohjelmointi](https://www.ohjelmointiputka.net/oppaat/opas.php?tunnus=cpp_ohj_01)

books/free-programming-books-he.md

@@ -4,7 +4,7 @@
   * [מערכות הפעלה](#מערכות-הפעלה)
   * [רשתות](#רשתות)
 * [Assembly](#assembly)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [Java](#java)
 * [Python](#python)
 
@@ -26,7 +26,7 @@
 * [ארגון המחשב ושפת סף](https://data.cyber.org.il/python/python_book.pdf) – ברק גונן, המרכז לחינוך סייבר (PDF)
 
 
-### <a name="c-sharp"></a>C#
+### <a name="csharp"></a>C\#
 
 * [מבוא לתכנות בסביבת האינטרנט בשפת C#](https://meyda.education.gov.il/files/free%20books/%D7%9E%D7%91%D7%95%D7%90%20%D7%9C%D7%AA%D7%9B%D7%A0%D7%95%D7%AA%20%D7%91%D7%A1%D7%91%D7%99%D7%91%D7%AA%20%D7%94%D7%90%D7%99%D7%A0%D7%98%D7%A8%D7%A0%D7%98%20090216.pdf) – מט״ח (PDF)
 

books/free-programming-books-hu.md

@@ -37,7 +37,7 @@
 * [Arduino programozási kézikönyv](http://avr.tavir.hu) - Brian W. Evans írása alapján fordította, kiegészítette és frissítette Cseh Róbert (PDF - regisztráció szükséges)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Fejlett programozási technikák](http://www.ms.sapientia.ro/~manyi/teaching/c++/cpp.pdf) - Antal Margit (PDF)
 

books/free-programming-books-id.md

@@ -2,7 +2,7 @@
 
 * [Android](#android)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [CodeIgniter](#codeigniter)
 * [Emacs](#emacs)
@@ -37,12 +37,12 @@
 * [Belajar Pemrograman C untuk Pemula](https://www.petanikode.com/tutorial/c/) - Ahmad Muhardian (:construction: *in process*)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Menguasai Pemrograman Berorientasi Objek Dengan Bahasa C#](https://mahirkoding.id/ebook-pemrograman-berorientasi-objek-c-pdf/)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Belajar C++ Dasar Bahasa Indonesia](https://github.com/kelasterbuka/CPP_dasar-dasar-programming) - Kelas Terbuka
 * [Koding C++ Dengan Qt](https://leanpub.com/koding-cpp-qt) *(Membutuhkan akun Leanpub atau email yang valid)*

books/free-programming-books-it.md

@@ -10,7 +10,7 @@
 * [Assembly Language](#assembly-language)
 * [BASH](#bash)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [CSS](#css)
 * [Database](#database)
@@ -97,12 +97,12 @@
 * [Tricky C](http://www.dmi.unict.it/diraimondo/web/wp-content/uploads/classes/so/mirror-stuff/Tricky_C.pdf) (PDF)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [ABC# - Guida alla programmazione](http://antoniopelleriti.it/wp-content/uploads/2019/04/ABCsharp-guida-alla-programmazione-in-csharp.pdf) - A. Pelleriti (PDF)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Corso C++ standard](http://didatticait.altervista.org/programmazione/CPP/CPP-dispense/CORSO_C.pdf) - (PDF)
 * [Il linguaggio C++](https://hpc-forge.cineca.it/files/CoursesDev/public/2012%20Autumn/Introduzione%20alla%20programmazioni%20a%20oggetti%20in%20C++/corsocpp.pdf) - (PDF)

books/free-programming-books-ja.md

@@ -271,7 +271,7 @@
 * [猫でもわかるプログラミング](http://kumei.ne.jp/c_lang) - 粂井康孝
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [C++11の文法と機能(C++11: Syntax and Feature)](https://ezoeryou.github.io/cpp-book/C++11-Syntax-and-Feature.xhtml) - 江添亮
 * [C++入門](https://www.asahi-net.or.jp/~yf8k-kbys/newcpp0.html) - 小林健一郎

books/free-programming-books-ko.md

@@ -57,7 +57,7 @@
 * [BeeJ's Guide to Network Programming - 인터넷 소켓 활용](https://blogofscience.com/Socket_Programming-KLDP.html)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [씹어먹는 C++](https://github.com/kev0960/ModooCode/raw/master/book/cpp/main.pdf) - 이재범 (PDF)
 
@@ -225,4 +225,3 @@
 ### Unicode
 
 * [번역 Unicode 이모티콘에 얽힌 이것저것 (이모티콘 표준과 프로그래밍 핸들링)](http://pluu.github.io/blog/android/2020/01/11/unicode-emoji/)
-

books/free-programming-books-langs.md

@@ -28,7 +28,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [BeanShell](#beanshell)
 * [BETA](#beta)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Chapel](#chapel)
 * [Cilk](#cilk)
@@ -462,7 +462,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [TONC GBA Programming - Game Boy Advance Development](http://www.coranac.com/tonc/text/toc.htm)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [C# Notes for Professionals](http://goalkicker.com/CSharpBook/) - Compiled from StackOverflow documentation (PDF)
 * [C# Programming](https://en.wikibooks.org/wiki/C_Sharp_Programming) - Wikibooks
@@ -485,7 +485,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Xamarin.Forms Succinctly](https://www.syncfusion.com/ebooks/xamarin-forms-succinctly) - Alessandro Del Sole
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [C++ Annotations](https://fbb-git.gitlab.io/cppannotations/) - Frank B. Brokken (HTML, PDF)
 * [C++ Core Guidelines](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md) - Editors: Bjarne Stroustrup, Herb Sutter

books/free-programming-books-nl.md

@@ -1,7 +1,7 @@
 ### Index
 
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [COBOL](#cobol)
 * [Java](#java)
 * [PHP](#php)
@@ -15,7 +15,7 @@
 * [Programmeren in C](https://nl.wikibooks.org/wiki/Programmeren_in_C) - Wikibooks
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Programmeren in C Sharp](https://nl.wikibooks.org/wiki/Programmeren_in_C_Sharp) - Wikibooks
 

books/free-programming-books-pl.md

@@ -5,7 +5,7 @@
 * [Assembly](#assembly)
 * [Bash](#bash)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Common Lisp](#common-lisp)
 * [Coq](#coq)
@@ -69,7 +69,7 @@
 * [Wgłąb języka C](http://helion.pl/online/wglab/wglab.zip) (ZIP)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Darmowy kurs C#](http://kurs.aspnetmvc.pl/Csharp)
 * [Kurs C#](http://zajacmarek.com/kurs-c-sharp/) - Marek Zając
@@ -78,7 +78,7 @@
 * [Wstęp do programowania w C#](http://c-sharp.ue.katowice.pl/ksiazka/c_sharp_wer2_0.pdf) - Anna Kempa, Tomasz Staś (PDF)
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [C++](https://pl.wikibooks.org/wiki/C++) - Wikibooks
 * [Język C++ – podstawy programowania](http://www.dz5.pl/ti/cpp/zz_dodatki/kurs_cpp_szczegolowy2.pdf) - Paweł Mikołajczak (PDF)

books/free-programming-books-pt_BR.md

@@ -7,7 +7,7 @@
 * [Android](#android)
 * [Assembly](#assembly)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Dart](#dart)
 * [Docker](#docker)
@@ -101,12 +101,12 @@
 * [Projeto de Algoritmos em C](http://www.ime.usp.br/~pf/algoritmos/)
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [C# e Orientação a Objetos](https://www.caelum.com.br/apostila-csharp-orientacao-objetos/) - Caelum
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Apostila Linguagem C++](http://www.ime.usp.br/~slago/slago-C++.pdf) - Silvio Lago (PDF)
 * [Estrutura de Dados](http://calhau.dca.fee.unicamp.br/wiki/images/0/01/EstruturasDados.pdf) (PDF)

books/free-programming-books-ru.md

@@ -9,7 +9,7 @@
 * [Assembly](#assembly)
 * [Bash](#bash)
 * [C](#c)
-* [C#](#c-sharp)
+* [C#](#csharp)
 * [C++](#cpp)
 * [Clojure](#clojure)
 * [CoffeeScript](#coffeescript)
@@ -143,15 +143,15 @@
 * [Язык Си в примерах](https://ru.wikibooks.org/wiki/Язык_Си_в_примерах) - Викиучебник
 
 
-### C Sharp
+### <a name="csharp"></a>C\#
 
 * [Паттерны проектирования в C# и .NET](https://metanit.com/sharp/patterns) - Евгений Попов
 * [Полное руководство по языку программирования С# 7.0 и платформе .NET 4.7](https://metanit.com/sharp/tutorial) - Евгений Попов
 * [Сетевое программирование в С# и .NET](https://metanit.com/sharp/net) - Евгений Попов
 * [Design Patterns via C#](http://itvdn.com/ru/patterns) - Александр Шевчук, Дмитрий Охрименко, Андрей Касьянов (PDF) *(Требуется аккаунт)*
 
 
-<h3 id="cpp">C++</h3>
+### <a name="cpp"></a>C++
 
 * [Введение в язык программирования С++](http://lib.ru/CPPHB/cpptut.txt_with-big-pictures.html) - Бьерн Страуструп
 * [Введение в язык Си++](http://stolyarov.info/books/cppintro) - Андрей Столяров (PDF)