Redesigned new room creation (fixes #98)

* Changes minimum window width
* Uses StackSwitcher-like setup instead of dropdown
1 job for master in 6 minutes and 58 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
failed #27139
flatpak

00:06:58

 
Name Stage Failure
failed
flatpak Test
Exporting share/icons/hicolor/32x32/apps/org.gnome.Fractal.png
Exporting share/icons/hicolor/24x24/apps/org.gnome.Fractal.png
Exporting share/icons/hicolor/symbolic/apps/org.gnome.Fractal-symbolic.svg
Please review the exported files and the metadata
Committing stage finish to cache
Pruning cache
$ flatpak build-export repo app
error: min-free-space-percent '3%' would be exceeded, 922.0 MB available
ERROR: Job failed: exit code 1