XEP-0280: include 0184 ACKs and 0085 CSNs

xep-0280.xml

@@ -283,6 +283,7 @@
     <ul>
       <li>it is of type "chat".</li>
       <li>it is of type "normal" and contains a &lt;body&gt; element.</li>
+      <li>it contains payload elements typically used in IM (&xep0184;, &xep0085;).</li>
       <li>it is of type "error" and it was sent in response to a &MESSAGE; that was eligible for carbons delivery (Note that as this would require message tracking and correlation on the server, it is unlikely to be generally appropriate for most implementations).</li>
       <li>it matches the MUC-related rules outlined below.</li>
     </ul>