Support for `ruff`

[yasirroni]

This is a separate issue from #1466 to track ruff support. This is also related to relative import #1537.

[jph00]

@yasirroni the nbdev3 extensions mechanism is now ready, so you can create a ruff extension. Here's the nbdevblack extension so you can see what's needed - it's <10 lines of code:
https://github.com/AnswerDotAI/nbdevblack/blob/main/nbdevblack/__init__.py