gtk-demo: Set an accessible role

Set the expected accessible role on the tagged entry
widget in the demo of the same name. Accessible tools
may decide to ignore widgets that have the wrong role,
so setting an appropriate role is important.

demos/gtk-demo/demotaggedentry.c

@@ -116,6 +116,7 @@ demo_tagged_entry_class_init (DemoTaggedEntryClass *klass)
 
   gtk_widget_class_set_layout_manager_type (widget_class, GTK_TYPE_BOX_LAYOUT);
   gtk_widget_class_set_css_name (widget_class, "entry");
+  gtk_widget_class_set_accessible_role (widget_class, GTK_ACCESSIBLE_ROLE_TEXT_BOX);
 }
 
 static GtkEditable *