[orgweb] Making the git repo URL more visible

[Adam Porter]

Hi Bastien, Timothy, et al,

Just now I found myself needing to look up the URL of the Org git repo,
and it seemed a bit harder than it ought to be.  It'd be nice if there
were a prominent "source code" link on the front page, but I remembered
that it was somewhere on the "Contribute" page, so I opened that.

When it loaded, I still overlooked the URL to the git repo.  I was
expecting to see some kind of "Source Code" header, or "git repo" link,
but instead the link is "The Org Codebase", and it's not under a header
or near any other text like "source code" or "git repo", so it seems
easy to overlook:

Other FOSS projects's sites seem to make their source code repo links
very prominent; could Org's web site do that too?  :)

--
Thanks,
Adam