Update free-courses-en.md (#9574)

Added Javascript Playlist

courses/free-courses-en.md

@@ -831,6 +831,7 @@
 * [Javascript course](https://www.youtube.com/playlist?list=PLRAV69dS1uWSxUIk5o3vQY2-_VKsOpXLD) - Hitesh Choudhary
 * [Javascript Essentials](https://www.udemy.com/javascript-essentials/) - Lawrence Turton (Udemy)
 * [Javascript Fundamentals](https://www.udemy.com/course/javascriptfundamentals) - Bharath Thippireddy (Udemy)
+* [JavaScript Leetcode](https://www.youtube.com/playlist?list=PLRKOqqzwh75hcG_D4xjUgbg_BAF3MLtoh) - Endeavour Monk
 * [JavaScript Mini Course 2020](https://www.udemy.com/course/javascript-essentials-mini-course/) - Kalob Taulien (Udemy)
 * [JavaScript Tutorial for Beginners](https://www.youtube.com/playlist?list=PL4cUxeGkcC9i9Ae2D9Ee1RvylH38dKuET) - The Net Ninja
 * [JavaScript Tutorial for beginners](https://www.youtube.com/watch?v=W6NZfCO5SIk) - Moshfegh Hamedani (Programming with Mosh)