Added link of YouTube playlist for Core Java Interview Questions. (#9656)

* Added link of YouTube palylist for Core Java Interview Questions.

* Updated Youtube Playlist for Java resource.

courses/free-courses-en.md

@@ -804,6 +804,7 @@
 * [Learn how to program: Java](https://www.learnhowtoprogram.com/java-june-2017) - Epicodus Inc.
 * [Learn Java](https://www.sololearn.com/learning/1068) - Sololearn *(email address required)*
 * [Learn Java Programming](https://www.programiz.com/java-programming) - Programiz
+* [Most Asked Core Java Frequently Asked Questions](https://www.youtube.com/playlist?list=PLyHJZXNdCXscoyL5XEZoHHZ86_6h3GWE1) - Code Decode
 * [Object Oriented Programming (OOP) In Java Course](https://www.youtube.com/playlist?list=PL9gnSGHSqcno1G3XjUbwzXHL8_EttOuKk) - Kunal Kushwaha
 * [Object-Oriented programming with Java, part I](https://moocfi.github.io/courses/2013/programming-part-1/)
 * [Object-Oriented programming with Java, part II](https://moocfi.github.io/courses/2013/programming-part-2/)