Codemetapy

Previous release was a bit premature, there was a bug related to 4 still that has now been fixed.

* parse dependency versions and store them explicitly; don't stumble over extras (they will be processed as any other dependency, the 'extra' information bit does not get converted. 4
* added a ``-no-extras`` parameter that disregards all the extras. 4

Minor bugfix release: do add duplicate entrypoints

Minor bugfix release: do not reset entrypoints when chaining

This release makes some changes to the way codemetapy works:
* Instead of parsing pip output, the tool now uses importlib.metadata to query for metadata. As metadata is read after installation, this work regardless of how the metadata was initially specified (setup.yp, setup.cfg or pyproject.toml)

New features:
* Added an output file parameter (``-O``)
* Added an integration hook for setuptools, allowing users to add a codemeta command to setup.py

Fixes:
* Prevent duplicates in authors and other fields

Minor update to entrypoint extension: attempt to automatically read the docstring for each entrypoint and use it as a description for the entrypoint metadata