prepare publication

[ranocha]

Since we're adding more features to this repo, it's getting more interest from others. Thus, it would be nice to polish it a bit - so that we can also prepare a software paper in the future. I have started this process in this PR.

@JoshuaLampert If you're fine with this, could you maybe list some breaking changes in the NEWS.md file?

[JoshuaLampert]

Thanks a lot for initiating that! I will fill the NEWS.md file with the changes from the last releases.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.57%. Comparing base (935081c) to head (1a3aa96). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #137 +/- ## ======================================= Coverage 97.57% 97.57% ======================================= Files 20 20 Lines 1569 1569 ======================================= Hits 1531 1531 Misses 38 38 ```

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[JoshuaLampert]

@JoshuaLampert If you're fine with this, could you maybe list some breaking changes in the NEWS.md file?

I filled the NEWS.md file. Please have a look if this looks fine to you.

[ranocha]

Let's see how the rendered changelog looks in the docs. If it's fine, I'm fine merging this PR

[JoshuaLampert]

The changelog looks nice, I think.

[ranocha]

I adapted the text in the code of conduct so that the links are better integrated in the markdown text.

[ranocha]

The changelog looks nice, I think.

I agree - nice work 👍