Add icon property to README

README.md

@@ -31,6 +31,7 @@ feed:
   content_limit: 140
   content_limit_delim: ' '
   order_by: -date
+  icon: icon.png
 ```
 
 - **type** - Feed type. (atom/rss2)
@@ -41,3 +42,4 @@ feed:
 - **content_limit** - (optional) Default length of post content used in summary. Only used, if **content** setting is false and no custom post description present.
 - **content_limit_delim** - (optional) If **content_limit** is used to shorten post contents, only cut at the last occurrence of this delimiter before reaching the character limit. Not used by default.
 - **order_by** - Feed order-by. (Default: -date)
+- **icon** - (optional) Custom feed icon. Defaults to a gravatar of email specified in the main config.