A new javascript for a mobile menu has been implemented (inspired by mmenu-js).

Usage:

<a href="#" data-mobile_menu="show">Menu</a>

...

<nav id="mobile-menu" style="display:none">
    <ul>
        <li>
            <a href="...">Link1</a>
            <ul>
                // next level
            </ul>
        </li>
        // more links
    </ul>
</nav>
<script>
    require(["jquery", "mobile-menu"], function($, Menu){   
        Menu.init("#mobile-menu", {
            position: "right"   // optional - default is "left"
        })
    })
</script>