Add fediverse:creator meta tag

As per this article [1].

[1]: https://rknight.me/blog/setting-up-mastodon-author-tags/

app/views/shared/_head.html.erb

@@ -6,6 +6,7 @@
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <meta name="keywords" content="ruby rails software development london" />
 <meta name="format-detection" content="telephone=no">
+<meta name="fediverse:creator" content="@[email protected]" />
 
 <% unless css_naked_day? %>
 <%= stylesheet_link_tag 'application' %>