integrate files with serving (even though ugly)

frontend/index.html

@@ -24,6 +24,7 @@
             flex-direction: column;
             align-items: center;
             justify-content: center;
+            background-color: transparent;
         }
     </style>
 </head>
@@ -38,6 +39,7 @@
             <input type="button" id="shortenButton" value="Submit">
         </div>
         <div id="output-container"></div>
+        <div id="error-container"></div>
     </div>
     <script src="index.js"></script>
 </body>