Added Redux Toolkit course (#7653)

* added two new javascript books that are free

* added two new javascript books that are free

* added free reat courses

* added free reat courses

* Update free-courses-en.md

* added redux toolkit tutorial

* added redux toolkit tutorial

* Update free-courses-en.md

courses/free-courses-en.md

@@ -751,6 +751,7 @@
 
 * [Getting Started with Redux](https://egghead.io/courses/fundamentals-of-redux-course-from-dan-abramov-bd5cc867)
 * [Learn Redux](https://learnredux.com) - Wes Bos (email address *requested*)
+* [Redux Toolkit Tutorial](https://youtube.com/playlist?list=PLC3y8-rFHvwiaOAuTtVXittwybYIorRB3) - Codevolution
 
 
 #### Svelte