bpo-22021: Update root_dir and base_dir documentation in shutil (GH-10367)


Also added an example in shutil in order to make more clear how they are to be used.

Initially reported by Weinan Li on bpo.
(cherry picked from commit 7633371dace67aaa21eb4b86f889441571ec4167)

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>
1 file changed