Move our PathLike below even TYPE_CHECKING imports

The benefits are that putting imports before newly introduced
names (other than names like __all__) is recommended by PEP-8, and
that git.types.PathLike is not equivalent to os.PathLike and
introducing it after all imports may help avoid obscuring this.

Author: EliahKagan

git/types.py

@@ -38,13 +38,13 @@
 # else:
 #     from typing_extensions import TypeGuard  # noqa: F401
 
-PathLike = Union[str, "os.PathLike[str]"]
-"""A :class:`str` (Unicode) based file or directory path."""
-
 if TYPE_CHECKING:
     from git.repo import Repo
     from git.objects import Commit, Tree, TagObject, Blob
 
+PathLike = Union[str, "os.PathLike[str]"]
+"""A :class:`str` (Unicode) based file or directory path."""
+
 TBD = Any
 """Alias of :class:`~typing.Any`, when a type hint is meant to become more specific."""