before_quit_hook: new hook

before_quit_hook: new hook

confirm-quit: removed command

  To get a quit confirmation, put the following in your rc:

   add_hook("before_quit_hook",
            function () {
                var w = get_recent_conkeror_window();
                var result = (w == null) ||
                    "y" == (yield w.minibuffer.read_single_character_option(
                        $prompt = "Quit Conkeror? (y/n)",
                        $options = ["y", "n"]));
                yield co_return(result);
            });