Add setup.py and pyproject.toml as activation triggers/package definitions for Python/pip

[Freso]

requirements.txt should generally only be used to freeze dependencies for deployment purposes, general non‐to‐the‐version specific dependencies should be given in setup.py or (since PEP 517) pyproject.toml.

Right now license_finder only recognises requirements.txt as a package definition, while both setup.py and pyproject.toml are (or should be!) much more of a canon package definition than requirements.txt is. All three can also exist together.

[eode]

Very much missing this feature.

Note that the only way (at least, that I've found) to acquire the full list of dependencies (accurately) is to create a python venv, install the project into that, and do a pip freeze --local from within the venv -- which then effectively generates a requirements.txt.

[xtreme-shane-lattanzio]

Hey @eode ! I welcome any PRs to add this! Since we do not actively have this usecase, we look to the community to add new things like this to make sure that it satisfies their situation

[dflock]

This is also needed to support python projects which use Poetry instead of pip: #943