Adopt openstack/governance-website as TC repo

The openstack/governance-website drives the top index content
for governance.openstack.org, and is driven by the TC chair.
It's a bit of an oversight that it's not listed yet as a TC repo.

Change-Id: I5673e1b61ce4f622aff910169c1c568b786a8343

reference/technical-committee-repos.yaml

@@ -8,3 +8,4 @@ Technical Committee:
   - repo: openstack/service-types-authority
   - repo: openstack/election
   - repo: openstack/goal-tools
+  - repo: openstack/governance-website