fishbowl: Add a menubutton demo

This reveals some issues with the position tracking.
10 jobs for master in 29 minutes and 50 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #307062
fedora-x86_64

00:08:14

passed #307063
win32
msys2-mingw32

00:13:02

 
  Flatpak
manual #307064
allowed to fail manual
flatpak-manual:demo
manual #307068
allowed to fail manual
flatpak-manual:icon-browser
manual #307066
allowed to fail manual
flatpak-manual:widget-factory
passed #307065
flatpak-master:demo

00:05:40

passed #307069
flatpak-master:icon-browser

00:10:13

passed #307067
flatpak-master:widget-factory

00:05:33

 
  Deploy
passed #307070
pages

00:06:31

passed pages:deploy

00:00:01