Update README.md

DataStructures/README.md

@@ -7,3 +7,4 @@ This part considers the following 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)
+  * [Bit arrays](https://github.com/0xAX/linux-insides/blob/master/DataStructures/bitmap.md)