add binary_tree_traversals.py to data_structures (#3297)

* add binary_tree_traversals.py to data_structures

I have added some interesting binary tree traversing methods.

* Fixed error

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Doctests and type hints

* Add spaces

* Update binary_tree_traversals.py

* black exclude data_structures/binary_tree/binary_tree_traversals.py

* Add spaces again

* Update binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>