Add requires-python metadata

[matthewfeickert]

• Add requires-python metadata through the addition of setuptools's python_requires in setup.py.

  • c.f. https://peps.python.org/pep-0621/#requires-python

• The addition of requires-python is to provide guards to keep older CPython versions from installing releases that could contain unrunnable code.

[matthewfeickert]

@andhus this is ready for review. Please let me know if you have any questions.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (4842a71) to head (aa3d4fb).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #28 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 2 2 Lines 194 192 -2 Branches 34 34 ========================================= - Hits 194 192 -2 ```

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[matthewfeickert]

Thanks @andhus! Would you be willing to make patch releases of scantree and dirhash with these in?

[andhus]

Thanks @andhus! Would you be willing to make patch releases of scantree and dirhash with these in?

Done ✅