demo: Bundle the icons representing the widgets

This also put the carousel icon in the right orientation so we don't
have to flip its rotation logic in the demo.

Fixes GNOME/libhandy#237
11 jobs for icons in 13 minutes and 37 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed api-visibility #846104

00:00:12

passed build-debian-clang #846106

00:02:53

passed build-debian-gcc #846105

00:03:20

passed build-fedora-gcc #846107

00:03:25

passed build-flatpak #846108
flatpak

00:01:17

passed build-flatpak-glade #846109
flatpak

00:03:51

 
  Test+Docs
passed build-gtkdoc #846110

00:02:15

passed unit-test #846111

00:03:43

44.0%
 
  Package
passed package-debian-buster #846112

00:03:09

 
  Test Package
passed autopkgtest-debian-buster-package #846113

00:02:50

passed lintian-debian-buster-package #846114

00:01:04