enable additional file types and add demo files

public/index.html

@@ -31,6 +31,7 @@
     <div id="root">
         <h1>Demo page</h1>
         <p>If you are seeing this then the server is working :)</p>
+        <p><a href="/includetest.html">Click here</a> to see an example of including css and js as separate files</p>
         <!-- <<LINKS>> -->
     </div>
 </body>