Added usage to readme

Author: WyriHaximus

README.md

@@ -15,6 +15,10 @@ To install via [Composer](http://getcomposer.org/), use the command below, it wi
 composer require api-clients/middleware-delay 
 ```
 
+# Usage
+
+[See the transport package how to use this middleware.](https://github.com/php-api-clients/transport#middleware)
+
 # License
 
 The MIT License (MIT)