added: javascript course. (#6233)

Add javascript course from Florin Pop Youtube channel.

courses/free-courses-en.md

@@ -470,12 +470,15 @@
 * [Functional Programming in Javascript](https://www.youtube.com/playlist?list=PL0zVEGEvSaeEd9hlmCXrk5yUyqUag-n84) - Mattias Petter Johansson «Fun Fun Function» (Youtube)
 * [Intro to JavaScript ES6 programming](https://www.youtube.com/playlist?list=PL-xu4i_QDSxcoDNeh8rx5-pHCCTOg0XsI)
 * [Intro To JavaScript Unit Testing & BDD](https://www.youtube.com/watch?v=u5cLK1UrFyQ) - Traversy Media
+* [Javascript Array Methods](https://youtube.com/playlist?list=PLgBH1CvjOA62PBFIDq55-S6Beivje30A2) - Florin Pop (YouTube)
+* [Javascript Coding Challenges](https://youtube.com/playlist?list=PLgBH1CvjOA63ROz8Wqd7RDD0qpvGXF8x5) - Florin Pop (YouTube)
 * [Javascript course](https://www.youtube.com/playlist?list=PLRAV69dS1uWSxUIk5o3vQY2-_VKsOpXLD) - Hitesh Choudhary
 * [Javascript Essentials](https://www.udemy.com/javascript-essentials/) - Lawrence Turton (Udemy)
 * [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
 * [Javascript30](https://javascript30.com) - Wesbos
 * [Learn how to program: JavaScript](https://www.learnhowtoprogram.com/javascript) - Epicodus Inc.
+* [Learn JavaScript](https://youtube.com/playlist?list=PLgBH1CvjOA636I8hnHSyuOnX341XQrBth) -  Florin Pop (YouTube)
 * [Learn JavaScript - Full Course for Beginners](https://www.youtube.com/watch?v=PkZNo7MFNFg) -  Beau Carnes, freeCodeCamp.org (YouTube)
 * [Learn modern JavaScript](https://scrimba.com/learn/es6) - Beau Carnes (Scrimba) (Scrimba account *required*)
 * [Learn to Program in Javascript: Beginner to Pro](https://www.udemy.com/course/programming-in-javascript) - Raghavendra Dixit (Udemy)