First version of Cuirass status frontend is attached (renamed from "index.html").

It displays, for a given project and jobset, a list of the latest finished builds
and the latest queued builds.  It also updates this list from time to time (every
minute or so).

For some reason, Cuirass only returns one project and jobset for the "jobsets"
request, so the HTML SELECTs will never contain more than one each :P

I can't find a way to get Cuirass to return a list of failed builds so that's
not supported.

To test it, you need to

(1) put it somewhere on https://berlin.guixsd.org/ in order not to be
"cross" (in this case, "URLPREFIX" can be simplified), or
(2) make Cuirass output special HTTP headers that specify the location
from where the scripting request is okay, or
(3) disable the cross-site scripting protection in icecat (Add-on "CORS
Everywhere").

Requires Javascript.