Fix building PyGithub with extra directories in source root

[treee111]

• closes [2.2.0] Extra directory in source tree trashes build #2887
• explicitly name the modules that should be build in pyproject.toml to tell the build system which modules it should build
• works when creating a empty dir with name temp in root of PyGithub
• for reference see https://setuptools.pypa.io/en/latest/userguide/package_discovery.html

[treee111]

feel free to test if this also works in your environment @kloczek

[EnricoMi]

LGTM!

[EnricoMi]

Tested locally, fixes the issue.

[EnricoMi]

@treee111 thanks for fixing this!

[kloczek]

feel free to test if this also works in your environment @kloczek

Just tested that and it works as expected 👍