Add release-openstack-sphinx-docs-infra template
Add release-openstack-sphinx-docs-infra template

We have some infra jobs that want to publish docs only on releases.

Change-Id: I236e4556249340a6a7fa1d82bb412a0e39259cc5

openstack-infra/openstack-zuul-jobs,openstack-infra/openstack-zuul-jobs