chore: Prepare for 0.9 release

[kylebarron]

• I agree to follow the project's code of conduct.
• I added an entry to the project's change log file if knowledge of this change could be valuable to users.
  • Usually called CHANGES.md or CHANGELOG.md
  • Prefix changelog entries for breaking changes with "BREAKING: "

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@benedikt-schaber are you good for a release?

[benedikt-schaber]

LGTM, thank you for preparing a release! :)

Just as a very small side note: Since it is a breaking change, I was wondering if we should try to, perhaps, include further breaking changes. I could look into what might be other qol-improvements, but I assume limiting the number of breaking version updates isn't yet a very big concern?

[kylebarron]

Do you see anything else you'd like to get into this release?

I don't think I'll have time in the short term to devote to any other features here, hence why I'm ok just making the new release. But if you want to make other changes we should hold off for a little.