Check for a course published event

[hectorsector]

write-a-ll-course/config.yml

Lines 343 to 349 in 06e10eb

	# 14
	- title: Publish your course to the sandbox environment
	description: Publish your course to the sandbox environment
	event: pull_request.closed
	actions:
	- type: respond
	with: congratulations.md

If https://github.com/github/learning-engineering/issues/276 is implemented, we can listen for an event that'll tell us when the course is published. This would be a great way improvement to the last step.