Archive tan and redirect people to ruff instead

[sciyoshi]

@jleclanche I'd like to propose archiving this repository and updating the README/description to point people to ruff instead.

Ruff's formatter is now stable, 99.9% compatible with and faster than Black, and supports tabs, so I personally see no reason to continue updating this fork.

[jleclanche]

I don't really see a reason to archive it until people widely stop using Black in favour of Ruff, but it's not actively updated so /shrug