Fix RSS feed description entries which broke when I swiched front-matter from overview: to description:

feed.xml

@@ -28,7 +28,7 @@ layout: null
 
       <item>
         <title>{{ post.title | xml_escape }}</title>
-        <description>{{ post.overview | xml_escape }}</description>
+        <description>{{ post.description | xml_escape }}</description>
         <pubDate>{{ post.publishdate | date_to_xmlschema }}</pubDate>
         <link>{{root}}{{ post.url }}</link>
         <author>{{ post.attribution }}</author>