Add support for GPG key in contact widget

layouts/partials/widgets/contact.html

@@ -22,6 +22,13 @@
       </li>
       {{ end }}
 
+      {{ with $.Site.Params.gnupg_key}}
+      <li>
+        <i class="fa-li fa fa-key fa-2x" aria-hidden="true"></i>
+        <code>gpg --recv-keys {{ . }}</code>
+      </li>
+      {{ end }}
+
       {{ with $.Site.Params.discussion }}
       <li>
         <i class="fa-li fa fa-comments-o fa-2x" aria-hidden="true"></i>