In case where uap-core isn't a git repo (e.g. git archive), use uap-core's `package.json` as a fallback for getting a version.

Apparently the way submodules repos are configured leads to the branches not being mirrored locally (?) As such, the release job's fallback of checking out `'master'` fails whether triggered[^1] or scheduled[^2].

[^1]: https://github.com/ua-parser/uap-python/actions/runs/13090871627
[^2]: https://github.com/ua-parser/uap-python/actions/runs/13092233962

Since the environment is required via `workflow_dispatch`, the only fallback is scheduled release in which case we're publishing to pypy.

Turns out `'master'` probably worked all along as a fallback, the
problem is that I was using `'master '`, with a trailing space, which
was not a branch git managed to find for obvious reason, and since I
carried the error into the fully qualified reference... is still
didn't work.

And manual triggers didn't have the issue because the tag was
`required`, so I'd have to input the tag by hand every time, and the
fallback value would be bypassed.

- fix the fallback value
- remove the requirement on `tag`, such that it's possible to manually
  trigger the action in a default state

- add classifier for cpython 3.13
- add classifier for graal (now that it's been merged)
- add pypy 3.11 to tox
- re2 still hasn't published for CPython 3.13 so exclude from tox

Fixes #257, fixes #265

Given ua-parser/uap-rust#29 and ua-parser/uap-rust#31, the wording of
the comparison needs to be updated to account for:

- The `regex` memory use being much improved.
- The `regex` runtime on devices being slightly improved, with the
  Python interface to `re2` not supporting custom atom lengths.

Closes #264

Don't remove the feature, don't remove the resolver, and keep the
resolver itself documented, but significantly de-emphasize `re2` by
removing it from the README and from examples: users should not be
encouraged to use it when they could use `regex`.