add-binary-tree-traversal

[ManuSharma0702]

Added binary_tree_traversal.py: Implemented a Node class to represent each node in the binary tree. Implemented inorder_traversal function to traverse the tree in in-order fashion. Implemented preorder_traversal function to traverse the tree in pre-order fashion. Implemented postorder_traversal function to traverse the tree in post-order fashion. Included driver code to demonstrate the functionality of the traversal methods.