Updated README

Added TO DO and Acknowledgements

Author: matakshay

AVL Tree/README.md

@@ -51,3 +51,14 @@ AVL Tree is a variant of the Binary Search Tree which uses rotation operations t
         </p>
     </li>
 </ul>
+<h2>To Do</h2>
+<ul>
+    <li>
+        Add copy constructor and overload the copy assignment operator for AVL Tree
+    </li>
+</ul>
+
+<h2>Acknowledgement</h2>
+<p align="justify">
+    I studied and referred many articles from the <a href="https://en.cppreference.com/w/">C++ Reference Documentation</a>, <a href="https://www.geeksforgeeks.org/">GeeksforGeeks</a> and <a href="https://www.wikipedia.org/">Wikipedia</a> while writing the code and preparing this document.
+</p>