Add RxJS YouTube playlist in English & Hindi free course (#5723)

* Added RxJS YouTube playlist in Hindi free course

* Added RxJS YouTube playlist in English free course

* Removed RxJS sub-category and merged course with JS category

* Removed RxJS sub-category and merged course with JS category

courses/free-courses-en.md

@@ -430,6 +430,7 @@
 * [learn:query](https://learnquery.infinum.co)
 * [Namaste 🙏 JavaScript: An In-Depth JavaScript Fundamentals Course](https://www.youtube.com/playlist?list=PLlasXeu85E9cQ32gLCvAvr9vNaUccPVNP) - Akshay Saini (YouTube)
 * [Programming Foundations with Javascript, HTML and CSS](https://www.coursera.org/learn/duke-programming-web) - Owen Astrachan, Robert Duvall, Andrew D. Hilton, Susan H. Rodger (Coursera)
+* [Understanding RxJS](https://youtube.com/playlist?list=PL55RiY5tL51pHpagYcrN9ubNLVXF8rGVi) - Academind
 * [Vanilla JavaScript](https://www.youtube.com/playlist?list=PLillGF-RfqbbnEGy3ROiLWk7JMCuSyQtX) - Brad Traversy, Traversy Media (YouTube)
 
 

courses/free-courses-hi.md

@@ -69,7 +69,7 @@
 
 * [JavaScript Tutorial \| Hindi](https://www.youtube.com/playlist?list=PLu0W_9lII9ajyk081To1Cbt2eI5913SsL) - Harry
 * [JavaScript Tutorial for Beginners (In Hindi)](https://www.youtube.com/playlist?list=PLwGdqUZWnOp1hqyT6h7pY0RlXIIGlE5U0) - Vinod Bahadur Thapa (Thapa Technical)
-
+* [RxJS Series (In Hindi)](https://youtube.com/playlist?list=PLLhsXdvz0qjI68a8tLUUMyXmNhl608mcn) - UX Trendz
 
 <h4 id="nextjs">Next.js</h4>