Wavelet tree (#4267)

* Added the matrix_exponentiation.py file in maths directory

* Implemented the requested changes

* Update matrix_exponentiation.py

* resolve merge conflict with upstream branch

* add new line at end of file

* add wavelet_tree

* fix isort issue

* updating DIRECTORY.md

* fix variable names in wavelet_tree and correct typo

* Add type hints and variable renaming

* Update data_structures/binary_tree/wavelet_tree.py

Add doctests to placate the algorithm-bot, thanks to @cclauss.

Co-authored-by: Christian Clauss <[email protected]>

* Move doctest to individual functions and reformat code

* Move common test array to the global scope and reuse in tests

* MMove test array to global scope and minor linting changes

* Correct the failing pytest tests

* MUse built-in list for type annotation

* Update wavelet_tree.py

* types-requests

* updating DIRECTORY.md

* Update wavelet_tree.py

* # type: ignore

* # type: ignore

* Update decrypt_caesar_with_chi_squared.py

* ,

* Update decrypt_caesar_with_chi_squared.py

Co-authored-by: Christian Clauss <[email protected]>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Aniruddha Bhattacharjee <[email protected]>