Add initial types to base and fun

[Yobmod]

Hi,
this add types to repo/base.py and repo/fun.py.

• All annotations are consistant according to both mypy and pyright.
• I've used an alias for Any type (TBD, 'to be determined') to show places where I was unsure of the type, but i'm sure it should be more specific than Any
• i've avoided changing any runtime code as much as possible, except:
  • i've used Union[str, os._pathlike] to annotate path arguments. Where this showed errors due to use of string-only methods, i've then wrapped the arg in str() within the function. This should mean they are all compatible with pathlib.Paths and pathlib.Purepaths, but that will require tests writing before its official.
  • Adding typeguards eg. where git_dir is initialised as None, then assigned later Type checking showed places that needed to be checked that it was actually a string and not None.
  • changed Except OSError, IOError to just OSError, as typechecking says it was redundant for python 3.