Add link to email that cfbot got patch from

[JelteF]

There's a little letter icon on the cfbot website next to each patch, that links back to the email thread (the link with the "envelope" symbol): http://cfbot.cputube.org/index.html

We should add that link somewhere on the commitfest app too. It should at least be on the patch detail page. Maybe we can fit one on the commitfest overview page too (we have limited space there though and I'm not sure this fits the usefulness bar).

[JelteF]

To make this work, the CFBot needs to be changed slightly to send this link.

[Anushre2005]

Hi

I’d like to try working on this issue.
From my understanding, this would require a small change in CFBot to expose the
email thread link, followed by a UI update in the CommitFest app to display it
(on the patch detail page at least).

Before I start, could you please confirm:
– Where the email thread URL should be exposed from CFBot?
– Whether you’d prefer this as one PR or split into CFBot + CommitFest PRs?

Thanks!