[ussuri][goal] Add CONTRIBUTING.rst

Story: 2007236
Task: 38552

Depends-On: https://review.opendev.org/#/c/726509/
Change-Id: If9333f9962c030edd0e22d77390b9515f2d2f70b

CONTRIBUTING.rst

@@ -0,0 +1,19 @@
+The source repository for this project can be found at:
+
+   https://opendev.org/openstack/puppet-barbican
+
+Pull requests submitted through GitHub are not monitored.
+
+To start contributing to OpenStack, follow the steps in the contribution guide
+to set up and use Gerrit:
+
+   https://docs.openstack.org/contributors/code-and-documentation/quick-start.html
+
+Bugs should be filed on Launchpad:
+
+   https://bugs.launchpad.net/puppet-barbican
+
+For more specific information about contributing to this repository, see the
+Puppet OpenStack contributor guide:
+
+   https://docs.openstack.org/puppet-openstack-guide/latest/contributor/contributing.html