ci: add Verible to GitHub Actions

Created by: cathales

This workflow will add suggestions as comments to the PRs when the modified lines have formatting issues.

Source: https://github.com/chipsalliance/verible-formatter-action/tree/main#automatic-review-on-prs-from-external-repositories

Note: the fail_on_formatting_suggestions option seems interesting; however it is not evaluated in PR workflows so we did not enable it in this configuration.