TYPING: Partial typing of Categorical
Adds some typing to ``Categorical``.

This PR does the simpler typing of ``Categorical``. In addition there are some more thorny typing that I've stayed away from for now to see if others can implement the basic types (list-likes etc.).
looks good, small comment, merge master and ping on green. Can we address my comment on `OrderedType` before merging? I don't think the definition in pandas._typing of that should add `object` because one method in the code base uses that as a temporary workaround can you rebase Rebased. lgtm. over to you @WillAyd  Great thanks a lot @topper-123 