Add option to exclude folders of a project (e.g. by one or more regexes)

[TysonAndre]

Some directories may have test failures immediately noticed, especially test folders (E.g. /tests/, vendor/phpunit and it's dependencies, etc.)

An exclude CLI flag with a regex to use to search the relative path within the folder would be useful.

e.g. to exclude /path/to/project/subdir/tests and /path/to/project/vendor/phpunit:

• -f /path/to/project --exclude '@/[tT]ests/|^vendor/phpunit/@'