Appends a custom item to the list of applications that is shown
in the popup.
The item name must be unique per-widget. Clients can use the
provided name as a detail for the
[signal@Gtk.AppChooserButton::custom-item-activated] signal, to add a
callback for the activation of a particular custom item in the list.
See also [method@Gtk.AppChooserButton.append_separator].
Appends a custom item to the list of applications that is shown in the popup.
The item name must be unique per-widget. Clients can use the provided name as a detail for the [signal@Gtk.AppChooserButton::custom-item-activated] signal, to add a callback for the activation of a particular custom item in the list.
See also [method@Gtk.AppChooserButton.append_separator].