feat: allow for requiring any scope.

[neverendingqs]

Currently, if requireScope is set to true, this action also assumes that scope is a non-empty list. If scope is not provided and a pull request title does not include one, the action fails with:

Error: Cannot read property 'join' of undefined

This is because the action assumes scope will be defined: https://github.com/amannn/action-semantic-pull-request/blob/master/src/validatePrTitle.js#L53-L59

This pull request proposes that scope doesn't have to be defined. If it is not, then any scope is permissible as long as one is provided in the pull request title.

Quality notes:

• Automated tests were TDD'ed and passing as expected
• Demo of action with current behaviour: feat: PR with no scope neverendingqs-sandbox/test-repo-amannn-action-semantic-pull-request#4
• Demo of action with proposed change throwing an error if the pull request does not include scope as expected: feat: PR with no scope  neverendingqs-sandbox/test-repo-amannn-action-semantic-pull-request#5
• Demo of action with proposed change passing if pull request includes a scope as expected: feat(scope): PR with scope. neverendingqs-sandbox/test-repo-amannn-action-semantic-pull-request#6

[amannn]

Really great PR, thanks a lot for your work!

Can you fix the reported lint errors? Afterwards this should be good to go.

[github-actions]

🎉 This PR is included in version 3.4.2 🎉

The release is available on GitHub release

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