[Docs] Clarify version number conventions wrt PEP440

[cdfarrow]

Summary

The setuptools' Version page gives a lot of example schemes that are not PEP440 compliant. I followed that page to create a post-release version number, but then it was rejected by PyPI. The page mentions PEP440 in passing in the opening paragraph, but it would be more helpful to explain that for certain situations (e.g. uploading to PyPI; what else?) PEP440 must be followed.

OS / Environment

No response

Additional Information

This would direct readers straight to the correct/recommended conventions rather than wasting their time reading irrelevant information.

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