Update starting-workflows.md

Author: rmcdaniel

docs/defining-workflows/starting-workflows.md

@@ -14,3 +14,5 @@ $workflow->start();
 ```
 
 Once a workflow has been started, it will be executed asynchronously by a queue worker. The `start()` method returns immediately and does not block the current request.
+
+You can also pass data to the workflow via the `start()` method. Any data you pass in will be sent to the workflow's `execute()` method.