Improve readme

readme.md

@@ -16,19 +16,37 @@ composer require rekurzia/yii2-papertrail-log-target
 
 ## Usage
 
-Add Sentry target to your configuration
+Add new target to your configuration:
 
 ```php
 $config['components']['log']['targets'] = [
     [
         'class' => Rekurzia\Log\PapertrailTarget::class,
         'levels' => ['error', 'warning'],
         'host' => 'logs[xxx].papertrailapp.com',
-        'port' => 1234,
+        'port' => '1234',
+        'additionalPrefix' => function() {
+            return Yii::$app->id;
+        },
     ],
 ];
 ```
 
+### Configuration options
+
+#### `host` and `port`
+
+Host and port of your Papertrail log destination.
+
+#### `additionalPrefix`
+
+**Optional.** A PHP callable which allows you to add additional prefix. Useful when `[ip][userI][sessionId]` is not
+enough. Setting as in example above, additional prefix `[yourApplicationId]` will be added. 
+
+#### `includeContextMessage`
+
+**Optional.** Whether to include also context message. Defaults to `false`.
+
 ## License
 
 MIT. See [license.txt](license.txt) file.