Gitea is quickly becoming the public face of Opendev, however it can
be difficult for visitors to understand how to propose changes (or
access already-proposed changes), and then assume everything on opendev
is read-only (which is the exact opposite of what we want to convey).
In the spirit of further integrating Opendev tooling, add a link to
on every repository to open proposed changes on Gerrit.
NB: the link is not I18n-ilized since there is no simple way to add a
new string there, and I did not want to use teh "Pull requests"
terminology.
Change-Id: I851a1e7d25556194947198a8f5534542d167c7f8
67408f6ead