defer app.js

Co-authored-by: Sebastian Beltran <bjohansebas@gmail.com>

Author: ShubhamOulkar

_includes/head.html

@@ -65,7 +65,7 @@
     {% else %}
     <meta property="twitter:image" content="https://expressjs.com/images/og.png">
     {% endif %}
-    <script data-cfasync="false" src="/js/app.js"></script>
+    <script data-cfasync="false" defer src="/js/app.js"></script>
     <script data-cfasync="false" defer src="/js/menu.js"></script>
     <script data-cfasync="false" defer src="/js/copycode.js"></script>
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.css" />