tests/ in pypi tarball

[pgajdos]

Hi!

Could i ask you for adding tests into release tarball? It can be used for testing the package after build.

[pgajdos]

Less important, but CHANGELOG.md would be convenient to have in tarball also.

[bgreen-litl]

I'm not against this. Off the top of my head, I think it would need to get added to the pyproject.toml packages section.

[bgreen-litl]

This is done in backoff 1.9.1 - both tests and CHANGELOG.md