document min, max kwargs to traitlets.{Int,Float}

[anntzer]

The min and max kwargs are "manually" implemented as kw-only args to Int and Float. As a consequence, they do not appear in the generated docs (https://traitlets.readthedocs.io/en/stable/trait_types.html#numbers) anywhere AFAICT. I think sphinx allows manually overriding the signature to e.g. use the Python3-format (Int(default_value=Undefined, allow_none=False, *, min=None, max=None, **kwargs)) in the docs.