use black for unified formatting

[orbeckst]

To make it easier for people to contribute and not be bogged down with formatting issues, I'd like to adopt black for formatting.

• Introducing Black to your project suggests to make the changes in a single big commit so that it can be excluded easily from git blame.
• adjust any linter options to work with black's opinion
• add a black linter to GitHub actions

Document for developers

• git pre-commit hook

After introduction of Black

• create .git-blame-ignore-revs as a follow-up