Add MFCC Feature Extraction Algorithm (#9057)

* Add MFCC feature extraction to machine learning

* Add standalone usage in comments

* Apply suggestions from code review

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

* Delete empty junk file (#9062)

* updating DIRECTORY.md

* updating DIRECTORY.md

* Delete empty junk file

* updating DIRECTORY.md

* Fix ruff errors

* Fix more ruff errors

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Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

* [main] Fix typo due to auto review change

* Add doctests for all functions

* Add MFCC feature extraction to machine learning

* Add standalone usage in comments

* Apply suggestions from code review

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

* [main] Fix typo due to auto review change

* Add doctests for all functions

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix some pre-commit issues

* Update review issues
* Remove types from docstring
* Rename dct
* Add mfcc docstring
* Add typing to several functions

* Apply suggestions from code review

* Update mfcc.py

* get_filter_points() -> tuple[np.ndarray, np.ndarray]:

* algorithm

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Co-authored-by: Christian Clauss <cclauss@me.com>
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>