Register __ as a dummy variable

[winstxnhdw]

ruff has a default Regex for recognising dummy variables in Python. See https://docs.astral.sh/ruff/settings/#lint_dummy-variable-rgx.

I often find myself writing something like this because I just want to let my args or kwargs passthrough.

def foo(text: str, *_, **__) -> str: ...

It would be nice if we added a setting similar to ruff that will let us set this behaviour.