Drupal 11 compatibility

Version queue_mail 8.x-1.6
Patch from #2 📌 Drupal 11 compatibility Active

It might be an idea to convert to Gitlab CI tests, and then try out this simple port in #2.

I've converted that, let's get the MR updated with the 8.x-1.x branch.

The tests with Drupal 11 are not happy about the configuration form, I'm not sure why at the moment, but looks like this needs work.

@el7cosmos brilliant, thanks!

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