feat(free-books): add licenses to 2 books;

resolves EbookFoundation#11355

Author: ATH42

Diff for: books/free-programming-books-langs.md

@@ -700,9 +700,9 @@ Books on general-purpose programming that don't focus on a specific language are
 
 ### Elixir
 
-* [30 Days of Elixir](https://github.com/seven1m/30-days-of-elixir) - Tim Morgan (HTML)
-* [Elixir School](https://elixirschool.com) (HTML)
-* [Elixir Succinctly, Syncfusion](https://www.syncfusion.com/ebooks/elixir-succinctly) (PDF, Kindle) (email address requested, not required)
+* [30 Days of Elixir](https://github.com/seven1m/30-days-of-elixir) - Tim Morgan (HTML) MIT
+* [Elixir School](https://elixirschool.com) (HTML) ALv2
+* [Elixir Succinctly, Syncfusion](https://www.syncfusion.com/ebooks/elixir-succinctly) (PDF, Kindle) (email address requested, not required) 
 * [Getting Started Guide](http://elixir-lang.org/getting-started/introduction.html) (HTML) [(PDF, MOBI, EPUB)](https://github.com/potatogopher/elixir-getting-started)
 * [Hands-on Elixir & OTP: Cryptocurrency trading bot](https://book.elixircryptobot.com) - Kamil Skowron (HTML)
 * [Joy of Elixir](https://joyofelixir.com) - Ryan Bigg (HTML) - [Source](https://github.com/radar/joyofelixir) *(:construction: in process)*