docs: update readme

Author: JacobBennett

README.md

@@ -30,6 +30,9 @@ protected $middleware = [
 
 ## Usage
 
+When you route a request through the `AddHttp2ServerPush` middleware, the response is scanned for any `link` or `script` tags that could benefit from being loaded using Server Push. 
+These assets will be added to the `Link` header before sending the response to the client. Easy!
+
 ## Change log
 
 Please see [CHANGELOG](CHANGELOG.md) for more information what has changed recently.