CI and downstream packagers have been using the Meson build for a while
now, and we checked that it's idempotent to the Autotools build.
Having two build systems in tree doesn't make maintaining and releasing
GTK any easier, even if it's the stable/frozen branch.
Setting up the icon and desktop file is a pretty central part
of making an application work, so we should do it for our example.
The fact that the examples are uninstalled makes this a little
more complicated.
Add a new example to the getting started part of the docs. The focus
of this example is on 'new stuff': GtkApplication, templates, settings,
gmenu, gaction, GtkStack, GtkHeaderBar, GtkSearchBar, GtkRevealer,
GtkListBox, GtkMenuButton, etc.
It is being developed in several steps. Each step is put in a separate
directory below examples/: application1, ..., application8. This is a
little repetitive, but lets us use the code of all examples in the
documentation.
