Add convenience cli options for displaying config path and folder

[roschly]

Implemented here:
https://github.com/roschly/shell_gpt/tree/cli-options
(not posted as a PR as per the contributing guidelines, since it is in no way urgent)

Inspired by:
https://github.com/charmbracelet/mods

Mods have two convenience options:
mods --settings: Open settings in your $EDITOR.
mods --dirs: Print the directories in which mods store its data

This would make it easier to find the configs, without having to consult the readme.