CSS

<link rel="preload" href="{{ 'custommenu.css' | asset_url }}" as="style" onload="this.onload=null;this.rel='stylesheet'">
    <noscript>
        <link rel="stylesheet" href="{{ 'custommenu.css' | asset_url }}">
    </noscript>


==================================
JS


    <script src="{{ 'jquery-2.1.1.min.js' | asset_url }}" async></script>
    <script src="{{ 'jquery-ui.min.js' | asset_url }}" async></script>