The usual pre-release minutia

[johenglisch]

• support python 3.8 (we don't need to do that but it was a 2-character fix so might as well)
• code style, linting, etc.
• fix the broken cldfbench command
• wanted to update the github action but there wasn't any – there is now
• make pip shut up about that stupid toml file they require now

[johenglisch]

Okay, CI takes 7½ minutes to run (after parallalising) but it works now.

[LinguList]

Thanks, @johenglisch! I suggest we merge this, and then we check with the one where I add all data (including co-authors, etc.)