WordPress Admin Menu: External link with Icon

gistfile1.txt

function add_custom_menu_item(){
    add_menu_page( 'Menu Item Title', 'Page Title', 'manage_options', 'page_slug', 'function', 'dashicons-icon', 1 );
}
add_action( 'admin_menu', 'add_custom_menu_item' );

function custom_menu_item_redirect() {

    $menu_redirect = isset($_GET['page']) ? $_GET['page'] : false;

    if($menu_redirect == 'page_slug' ) {
        wp_safe_redirect( home_url('/my-page') );
        exit();
    }

}
add_action( 'admin_init', 'custom_menu_item_redirect', 1 );