feature: Add user-defined `ignored_modules`

[axm2]

Is your feature request related to a problem? Please describe.

When loading a module via load() or load_git() or griffe check I would like to be able to ignore certain modules.

Describe the solution you'd like

I should be able to pass a list of modules to ignore or paths that griffe should skip when searching.

griffe check my_package --against 1.0 --ignore-modules __about__ test_module foo/not_used_in_production.py bar/*

Additional Context

I encountered this when griffe complained about a breaking change after I updated my package's version by bumping __version__ in __about__.py.