Create separate build and deploy workflows for intro website

[stickyPiston]

From #511:

sadserver/ansible/roles/intro_website/templates/deploy-intro-website.sh.j2

Lines 14 to 26 in bcdfc55

	# TODO
	# This script downloads the artifact of the latest successfully _completed_
	# workflow run, and as such the calling workflow must have finished before this
	# script attempts to download the related artifact for deployment.
	# It thus waits until the workflow which triggered this deploy has been completed,
	# such that this script does not download and deploy the previous version of the website.
	# The 'sleep 20' is a lazy fix, but not everything has to be perfect, and we
	# will transition to containerization soon anyway.
	# A better solution would be to split up the workflow into build and deploy
	# workflows, such that one calls the other. Then, the build workflow with
	# artifact will have completed once the deploy artifact - calling this script -
	# has started. Another advantage is that more workflows can trigger the deploy
	# seperately.