Add mastodon verification link

Author: mhagander

templates/index.html

@@ -3,6 +3,7 @@
 {%block title%}The world's most advanced open source database{%endblock%}
 {%block meta%}
   <meta name="description" content="The official site for PostgreSQL, the world's most advanced open source database" />
+  <link rel="me" href="https://fosstodon.org/@postgresql" />
 {%endblock%}
 {%block layoutblock%}
 <div class="jumbotron jumbotron-fluid pg-jumbotron">