Added Fast Inverse Square Root (#11054)

* Feat: Added Fast inverse square root

* Fix: Added typehint

* Fix: Added doctests that break the code, changed var name

* updating DIRECTORY.md

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

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* Fix: fixed length of docstring

* Update fast_inverse_sqrt.py

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