Add support for u-syndication of each entry, tracking where else it's been posted

templates/mf2/h-entry.hamlet

@@ -17,3 +17,7 @@
     <time .dt-updated datetime=#{timeUnfriendly updated} :published == updated:hidden>
       <i .fa.fa-pencil>
       #{timeFriendly updated}
+    $forall (E.Value url, E.Value icon, E.Value name) <- posses
+      <a .u-syndication href=#{url}>
+        <i .fa.fa-#{icon}>
+        #{name}