revert: got back to initial naming and added a marker

Added comment so that no one changes the Node class

Author: sanyamdogra

src/_DataStructures_/LinkedList/index.js

@@ -1,6 +1,7 @@
+// do not change the node class, you never know how many things it caan break! :) 
 class Node {
   constructor(data, next) {
-    this.my_data = data;
+    this.data = data;
     this.next = next;
   }
 }