Update free-courses-en.md (#8283)

Added new Next.js course

courses/free-courses-en.md

@@ -742,6 +742,7 @@
 
 #### Next.js
 
+* [Master Next JS by Building Real Projects](https://www.youtube.com/playlist?list=PL6QREj8te1P7gixBDSU8JLvQndTEEX3c3) - JavaScript Mastery
 * [Mastering Next.js](https://masteringnextjs.com)
 * [Next.js Tutorial for Beginners](https://youtube.com/playlist?list=PLC3y8-rFHvwgC9mj0qv972IO5DmD-H0ZH) - Codevolution