add footnotes

Author: neverRare

dist/index.html

@@ -168,7 +168,7 @@ <h1>
     <dialog id="error-box">
       <h1>An error has occurred</h1>
       <p>
-        This is not supposed to happen. If you're using an outdated browser,
+        This is not supposed to happen. If you're using an outdated* browser,
         please consider updating it. It might be due to that reason. Otherwise
         please consider reporting this. We respect user's privacy and so we rely
         on user-submitted bug reports. Here are the contact options:
@@ -199,6 +199,10 @@ <h1>An error has occurred</h1>
         <li>The following error message: <code id="error-code"></code></li>
         <li>Your browser and its version (optional).</li>
       </ul>
+      <p>
+        * We consider browsers that hasn't been updated for the last 2.5 years
+        to be outdated.
+      </p>
       <button id="error-close-button">Close</button>
     </dialog>
   </body>