Add modules to Jetpack menu

functions.php

/**
 * Admin menu changes
 */
function add_menus() {

	if ( class_exists( 'Jetpack' ) ) {
		add_action( 'jetpack_admin_menu', 'add_jetpack_menu' );
	}
}

add_action( 'admin_menu', 'add_menus', 5 );

/**
 * Add a sub-menu to Jetpack for the modules
 */
function add_jetpack_menu() {

	add_submenu_page(
		'jetpack',
		'Jetpack Modules',
		'Modules',
		'manage_options',
		'jetpack_modules',
		'jetpack'
	);
}