Add ruff linter and formatter.

[stankudrow]

I like using ruff: it is fast and is one tool that can replace as various linters, as formatters.

@Tinche , if you feel OK with ruff, I can open a PR in which ruff can replace black and flake8.

[Tinche]

Sure, I'd be open to that.

[stankudrow]

Cool, thanks.