Investigate if pre-merge checking works as expected in GitHub Actions

[CodeGat]

Description
Figure out if the on.pull_request.merge_group is all it's cracked up to be. This is going to be used to do heavier checks before a merge, after all reviews have been completed.

Possibly just try with a private repository, although it might only work for organisations. Check out https://github.blog/changelog/2022-08-18-merge-group-webhook-event-and-github-actions-workflow-trigger/

This issue blocks #69

[CodeGat]

See the above merged (via queue) for run details.
Merge Queue doesn't seem to be running the if: github.event_name == 'merge_group' checks. See this run specifically: https://github.com/ACCESS-NRI/test/pull/16.

In this case, Merge Groups seem to not be the correct way to go for expensive checks. In this case, we can still do the expensive checks as part of a regular on.pull_request.

Closing.