added gronsfeld cipher implementation (#11835)

* added gronsfeld cipher implementation

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

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* from string import ascii_uppercase

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

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* Update gronsfeld_cipher.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>