Add GitLab CI configuration

Are the failing phpunit tests in the merge request expected until this goes in?

@KarlShea Those failing tests are on D10 🐛 Tests failing when run against 10.x branch Needs work . I haven't had time to dig very deeply into those. Drupal CI is still passing since it is configured to run against D9.

If it was up to me, I would merge this and address the D10 issues in 🐛 Tests failing when run against 10.x branch Needs work . Thoughts?

Makes sense to me, I'd say go for it for all of these issues. I'm not familiar with how the CI pipelines are done for GitLab/Drupal anyways.

Automatically closed - issue fixed for 2 weeks with no activity.