scaling: Add GSettings for adjusting the height of the panel

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/679>

meson.build

@@ -70,6 +70,7 @@ else
   depdatadir = get_option('depdatadir')
 endif
 dbusdir = join_paths(depdatadir, 'dbus-1/interfaces')
+schemasdir = datadir / 'glib-2.0' / 'schemas'
 
 conf_data = configuration_data()
 conf_data.set_quoted('GETTEXT_PACKAGE', 'squeekboard')
@@ -111,3 +112,7 @@ subdir('protocols')
 subdir('src')
 subdir('tools')
 subdir('tests')
+
+gnome.post_install(
+    glib_compile_schemas: true,
+)