build: Include conftest.py and test assets in source distribution

[mgorny]

Include the conftest.py file and test assets in the source distribution archives explicitly. Otherwise, only test_*.py files are included, and they are insufficient to run tests.

[CLAassistant]

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[woodruffw]

Including these makes sense, thanks. Any chance we could do it via pyproject.toml instead of a separate MANIFEST.in, to keep to root directory cleaner?

[mgorny]

I don't think there's an explicit equivalent supported. I think using setuptools-scm to include all files from the repository could work, though.

[woodruffw]

#103 should do this. Thanks again for raising @mgorny!