Update and rename feed_by.xml to feed_by.html

assets/feed_by.xml → assets/feed_by.html

@@ -1,6 +1,6 @@
 ---
 layout: compress
-permalink: /feed_by.xml
+permalink: /feed_by.html
 ---
 
 {% assign posts_by_author = site.posts | where:"author", page.url.params.author %}