fix feed format

Signed-off-by: Nikhil Nigade <[email protected]>

feed.xml

@@ -2,12 +2,13 @@
 layout: null
 ---
 <?xml version="1.0" encoding="UTF-8"?>
-<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
+<rss version="2.0">
   <channel>
     <title>{{ site.title | xml_escape }}</title>
     <link>{{ site.url }}{{ site.baseurl }}/</link>
     <description>{{ site.description | xml_escape }}</description>
     <pubDate>{{ site.time | date_to_rfc822 }}</pubDate>
+    <lang>en</lang>
     <image>
       <url>{{ "/assets/images/appicon/apple-touch-icon.png" | absolute_url }}</url>
       <title>{{ site.title | xml_escape }}</title>