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

Story: 2007236
Task: 38552

Depends-On: https://review.opendev.org/#/c/726509/
Change-Id: I9aee594fc624eb1180aad1c51bbdc275156b33fd

openstack/puppet-trove,openstack/puppet-trove,openstack/puppet-trove