Course css (EbookFoundation#9941)

* Add Java and Kotlin free courses in pt-BR

* add css course

Author: carolruo

courses/free-courses-en.md

@@ -747,6 +747,7 @@
 * [CSS Tutorials](https://youtube.com/playlist?list=PLDyQo7g0_nsUjf046cCHKJ16U1SoXrElZ) - Dev Ed
 * [CSS3 tutorial for beginners \| Learn CSS3](https://www.udemy.com/course/css3-tutorial-for-beginners-learn-css3/) - Udemy
 * [Flexbox in 30 Days](https://github.com/samanthaming/Flexbox30) - Samantha Ming
+* [Gentle Introduction to CSS for Beginners](https://www.youtube.com/playlist?list=PLErOmyzRKOCptjkM-mOfveYlgKQEx1AAf) - Deborah Kurata
 * [Gentle Introduction to HTML for Beginners](https://www.youtube.com/playlist?list=PLErOmyzRKOCpmPEZIkblP-0sNufXbvXJL) - Deborah Kurata
 * [Get to know HTML Learn HTML Basics](https://www.udemy.com/course/html-online-course/) - Laurence Svekis (Udemy)
 * [HTML & CSS](https://www.youtube.com/playlist?list=PLillGF-RfqbZTASqIqdvm1R5mLrQq79CU) - Brad Traversy, Traversy Media