HandlerFeedGenerator: Improvements to make feed vlaid

template/quitesimple/feeds/atomentry

@@ -3,5 +3,6 @@
     <link href="{qswiki:var:entryurl}"/>
     <id>{qswiki:var:entryid}</id>
     <published>{qswiki:var:entrypublished}</published>
+    <updated>{qswiki:var:entryupdated}</updated>
     <content type="html">{qswiki:var:entrycontent}</content>
 </entry>