Add `pull_request` trigger to `merge_group` action #83675

	name: Is Pull Request

	# This job succeeds for every pull request. Then, in settings, we protect trunk
	# such that every commit to trunk must have this job succeed. This effectively
	# makes it such that no one can push directly to `trunk`, since only PRs can
	# include this check.

	# We need this because you can only forbid pushing to `trunk` based on branch
	# protection rules. We only utilize the "Require status checks to pass before
	# merging" branch protection rule. If we wanted every other normal "check" to NOT
	# be required, then there would be no "required check" which prevents pushing
	# to trunk. As a result, we have this little fake "check" which will always show
	# up on PRs to prevent direct commits to trunk.

	on:
	pull_request:
	types: [ opened, synchronize ]

	jobs:
	is-pull-request:
	name: 'Protect Trunk Branch'
	runs-on: ubuntu-latest
	steps:
	- name: Tells you that it's a pull request
	run: 'echo "This is a pull request 👍."'

Provide feedback