The homepage mentions a lot of technologies that OpenDev use, but
doesn't link to any of the running instances. This commit
adds links to review.opendev.org, etherpad.openstack.org and
the configuration for the opendev homepage itself, so that
it's easier to find things and to experience the technologies
it refers to.
Change-Id: Ia041ebbc558539955238bb4fdb4da868bf6f1dd8
1d07e57ab8