Closes #1954

Fixes #1956

This PR has two goals:

* Ensure that I, as a maintainer, do releases more consistently and with less effort.
* Enable other trusted members of the pypdf community and the py-pdf organization to make releases to PyPI. That should typically not be done, but is a last resort in case I become inactive.

What was done:

* A new repository secret `FLIT_PASSWORD` was created via PyPI. It is a PyPI token for pypdf.
* A Github Action `release.yaml` (this PR) was created.

## Hints

To ensure that you can write Markdown-style git tags, you can do this:

```
git config --global core.commentChar ";" 
```

## Testing

I used pdfly for that. Looks mostly fine. It especially published to PyPI.
See "TODO" for what is missing.

## TODO

* Make the release have rendered Markdown. I think I struggle with the fact that the body is a multi-line string ... maybe 🤔 
* Ensure the package is only pushed if it passes our test suite

## Resources

* https://github.com/actions/create-release
* https://flit.pypa.io/en/stable/cmdline.html#envvar-FLIT_INDEX_URL
* https://git-scm.com/docs/git-config#Documentation/git-config.txt-corecommentChar

Closes #1836

Bug Fixes (BUG):
-  Accept calRGB and calGray color_spaces (#1968)
-  Process 2bits and 4bits images (#1967)
-  Check for AcroForm and ensure it is not None (#1965)

Developer Experience (DEV):
-  Automate the release process (#1970)

[Full Changelog](3.12.1...3.12.2)