Move static metadata from setup.py to setup.cfg, add sdist check

[mwtoews]

This is an alternative proposal to #1426 following these setuptools instructions to move static metadata from setup.py to setup.cfg. Curious to see how the outcome of release.yml compares.

[coveralls]

Pull Request Test Coverage Report for Build 2538974489

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 84.215%

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Totals
Change from base Build 2531170575:	0.0%
Covered Lines:	2086
Relevant Lines:	2477

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💛 - Coveralls

[mwtoews]

Closing in favor of #1426, which embraces PEP 621 to store project metadata in pyproject.toml.