Lack of Pybtex Releases is hindering important fixes

[shyamd]

The lack of Pybtex releases is really problematic. While there have been a number of fixes merged, none of these have made it to PyPi. The last release was January 2021.

A couple of options:

• Use a pinned git version instead of a pypi version. This might be more brittle for some use cases where a user wants to use pybtex for something else, but those usecases should be rare or fixable by isolating the documentation env from the other need.
• Try CiteProc-Py
• Build python bindings for something like hayagriva for which I have already raised a feature request: [Feature] Python bindings typst/hayagriva#267