[ussuri][goal] Add CONTRIBUTING.rst
[ussuri][goal] Add CONTRIBUTING.rst

Story: 2007236
Task: 38552

Depends-On: https://review.opendev.org/#/c/726509/
Change-Id: Iffda75f8ba1a67f9595629ce3d4c888b69c7ece3

openstack/puppet-monasca,openstack/puppet-monasca,openstack/puppet-monasca,openstack/puppet-monasca,openstack/puppet-monasca