feat: ignore .gitignored files when running locally

[Kajiih]

I think there should be a flag in the CLI version to ignore files in .gitignore.

Actually, it's probably even better to ignore them by default and add a --no-ignore flag. For example, fd does this:

> fd --help
...
-I, --no-ignore
          Show search results from files and directories that would otherwise be ignored by
          '.gitignore', '.ignore', '.fdignore', or the global ignore file, The flag can be
          overridden with --ignore.
...

Probably related: https://github.com/cyclotruc/gitingest/issues/147 and https://github.com/cyclotruc/gitingest/issues/111#issuecomment-2581494975