Add an additional webhook event to trigger the eca check

One of our projects uses a branch protection rule with a merge queue and has the eca check as required status check defined. However, in such a case, the eca check is not actually performed as the merge queue sends a specific webhook event, see this comment

Please take a look at this ticket: https://github.com/eclipse-apoapsis/.eclipsefdn/issues/3#issuecomment-2007877538

A temporary solution will be to remove the eca check as required status check, but in the long term it would be great to support also such cases.