Added data structure course by mycodeschool (#4431)

* Added data structure course by mycodeschool

* link changed to playlist

free-courses-en.md

@@ -63,6 +63,7 @@
 ### Algorithms & Data Structures
 
 * [Berkeley University CS 61B: Data Structures](http://datastructur.es/sp16/)
+* [Data Structures](https://www.youtube.com/playlist?list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P) - mycodeschool
 * [Data Structures Easy to Advanced Course - Full Tutorial from a Google Engineer](https://www.youtube.com/watch?v=RBSGKlAvoiM) - William Fiset - (freeCodeCamp)
 * [IIT Bombay Foundation of Data Structures (CS213.1x)](https://courses.edx.org/courses/course-v1:IITBombayX+CS213.1x+1T2017/course/)
 * [MIT's Design and Analysis of Algorithms (Spring 2012)](https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-046j-design-and-analysis-of-algorithms-spring-2012) - Dana Moshkovitz, Bruce Tidor