[BridgeAbstract] Add getIcon

BridgeAbstract.md

@@ -7,6 +7,7 @@ To create a new Bridge extending `BridgeAbstract` you must specify some [basic m
 - [`getMaintainer`](#the-getmaintainer-function)
 - [`getName`](#the-getname-function)
 - [`getURI`](#the-geturi-function)
+- [`getIcon`](#the-geticon-function)
 
 Find a [template](#template) at the end of this file.
 
@@ -222,6 +223,16 @@ This function returns the URI to the destination site of a bridge.
 	}
 ```
 
+## The `getIcon` function
+
+This function returns the URI for an icon, used as favicon in the feeds. If no icon is specified by the bridge, RSS-Bridge will use the "default" location `static::URI . '/favicon.ico'` (i.e. "https://github.com/favicon.ico") which may or may not exist.
+
+```PHP
+	public function getIcon(){
+		return self::URI . '/favicon.ico';
+	}
+```
+
 ## Queried context
 
 The queried context is defined via `PARAMETERS` and can be accessed via `$this->queriedContext`.