Description:
Currently setup-python (v4) produces an error when trying to cache pip packages defined in a .pyproject.toml file instead of requirements.txt.

    - uses: actions/setup-python@v4
      with:
        cache: 'pip'

results in

Error: No file in /home/runner/work/EMAworkbench/EMAworkbench matched to [**/requirements.txt], make sure you have checked out the target repository

It would be great if pip packages defined in a .pyproject.toml file could also be cached, without a requirements.txt file present. Support for caching defined extras (optional dependencies) would also be great.

Justification:
setup-python should support projects following the latest build and configuration standards.

Are you willing to submit a PR?
Not at this moment