Add an ignore or exclude option for paths

[jhedstrom]

We are trying to run this against a theme that has external PHP libraries inside the directory (Pattern Lab in this case). When running the check, if we only specify the theme directory, all the external library code triggers failures.

It would be great to be able to specify an --ignore or an --exclude pattern so we could run against entire directories, but specify something like --ignore=pattern-lab/* or similar.

Note, I looked for info on changes made in #1 since I thought that might allow for exclusion patterns, but didn't see any relevant code changes there. (It appears phpstan.neon supports this option, but I wasn't sure how to specify that for drupal-check.)

[mglaman]

Not adding options to this project when PHPStan can be used directly