feature: remember settings for projects in a file called ".c2pconfig"

[mufeedvh]

Optionally, let the user save CLI flags for their projects in a file called .c2pconfig, which lets them do c2p . and it will pick up the inclusion/exclusion settings used inside the project directory frequently.

[ODAncona]

@mufeedvh This feature is essential and was requested by the owner of code2prompt python in order to merge the libraries. They should have similar APIs first.