Create feedback form for devhub

[samuelsidler]

Every page on devhub should have a link to a feedback form. For now, let's call it "Report an Issue" and let's put it in the header, on the right. I think it's fine for it to just be text for now.

The feedback form, per @coffee2code, should just be an open comment form, but should also include the referrer so we know what page the user is reporting an issue with. Comments will _not_ be displayed. However, Siobhan should get an email for every comment (siobhan@…). (She'll then pipe this into Slack.)

That means we need the following fields for the form: name, username, email, problem URL (autofilled via referrer, but editable), and comment form.

[DrewAPicture]

@samuelsidler Can we get an updated definition of the problem we're trying to solve?

It seems like when this ticket was created it was maybe to solicit something akin to beta feedback. I think funneling feedback through one person at this point would be unrealistic.

[DrewAPicture]

Related: #607

[samuelsidler]

The idea for issue reporting was to cover errors in both the code reference and developer handbooks (and even the dashicons page). If we have a better way to do that, let's do it. Feel free to hijack or close this ticket, if needed.

[coffee2code]

In 3787:

developer.wordpress.org: Explicitly indicate feedback is acceptable via the same form as user contributed notes.

See #981.
Fixes #607.

[obenland]

Feels to me like [3787] satisfied the intent of this ticket? Is the way it now works not good enough?

[samuelsidler]

[3787] only covers the code reference. This ticket covers the entirety of devhub, including documentation (handbooks).

[coffee2code]

Feedback for the code reference has been in place for awhile, so that aspect should be covered.

As for handbooks, we'll enable the comment form for those pages. Comments won't be publicly visible, only used as a means to submit feedback about the page to the site admins. We'll probably want to build filters into the backend so moderators can see the feedback for a particular handbook.

As for regular pages, there is really only one meaningful page at present: the dashicons page. I consider feedback for that page something more appropriately handled as a meta.trac ticket.

[tellyworth]

Duplicate of #5738.