Use `content:encoded` in Rss feeds

when using ShowFullTextinRSS

layouts/_default/rss.xml

@@ -11,7 +11,7 @@
 {{- $pages = $pages | first $limit -}}
 {{- end -}}
 {{- printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\"?>" | safeHTML }}
-<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
+<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:content="http://purl.org/rss/1.0/modules/content/">
   <channel>
     <title>{{ if eq  .Title  .Site.Title }}{{ .Site.Title }}{{ else }}{{ with .Title }}{{.}} on {{ end }}{{ .Site.Title }}{{ end }}</title>
     <link>{{ .Permalink }}</link>
@@ -41,7 +41,7 @@
       <guid>{{ .Permalink }}</guid>
       <description>{{ with .Description | html }}{{ . }}{{ else }}{{ .Summary | html }}{{ end -}}</description>
       {{- if .Site.Params.ShowFullTextinRSS }}
-      <content>{{ .Content | html }}</content>
+      <content:encoded>{{ (printf "<![CDATA[%s]]>" .Content) | safeHTML }}</content:encoded>
       {{- end }}
     </item>
     {{- end }}