Add async JavaScript

public/assets/enhancements.js

@@ -0,0 +1,10 @@
+// Check if DOM has already loaded as we're loading async
+if(['interactive', 'complete'].indexOf(document.readyState) >= 0) {
+  init();
+} else {
+  document.addEventListener('DOMContentLoaded', init);
+}
+
+// When DOM is ready
+function init() {
+}

views/index.html

@@ -39,5 +39,6 @@
       </div>
     </footer>
 
+    <script src="/assets/enhancements.js" async></script>
   </body>
 </html>