Add release notes for 0.0.9

[jbusecke]

There were no release notes for v0.0.8 and v0.0.9. I bumped the current version in #123 but I assume there is more content missing?

[TomNicholas]

They are missing because those were debug attempts, not really real releases. I'm not sure what best practice is now.

[jbusecke]

Ah then I would probably just delete these releases entirely? But maybe that is not the best way to do this?

[keewis]

you can yank a release on PyPI, such that installers avoid installing it but someone who pinned their environment to exactly that version can still install it.

For future debug attempts, you can create versions with suffixes, like the pre-release suffixes: rc0, a0, b0. Those are only installed when explicitly requested (just like yanked releases, but without the extra work to mark them as such), and you don't need to update the release notes.