Update README.md

DataStructures/README.md

@@ -6,3 +6,4 @@ Linux kernel provides implementations of a different data structures like linked
 This part considers these data structures and algorithms.
 
   * [Doubly linked list](https://github.com/0xAX/linux-insides/blob/master/DataStructures/dlist.md)
+  * [Radix tree](https://github.com/0xAX/linux-insides/blob/master/DataStructures/radix-tree.md)