feat: Add rel="me" link for mastodon

theme/templates/inc/footer.html.j2

@@ -110,6 +110,7 @@
         </a>
         <a href="https://fosstodon.org/@funkwhale"
            title="via Mastodon"
+           rel="me"
            class="funkwhale button is-outline icon-only">
           <i class="fa fa-mastodon" aria-hidden="true"></i>
         </a>