Review files included in release package

[Juarez Rudsatz]

Context

• During the build of the package, a bunch of files and folders from the git clone are being included in the source tarball
• We should tweak to include only the required files in:
  • pyproject.toml
  • setup.py
  • MANIFEST.in

[Juarez Rudsatz]

Additionally, there are some warnings in the PyPI release pipeline that are worth checking:

setuptools_scm/git.py:105: UserWarning: "/home/runner/work/petl/petl" is shallow and may cause errors

warning: no files found matching '*.txt' under directory 'docs'