add mastodon link with rel=me

frontend/index.html

@@ -33,6 +33,7 @@
   </noscript>
   <div id="root"></div>
   <script type="module" src="/src/index.tsx"></script>
+  <a rel="me" href="https://mastodon.social/@fediversespace" style="display: none">Mastodon</a>
 </body>
 
 </html>