Update README.md

Fix missing event url in create_application

Author: sammachin

README.md

@@ -173,7 +173,7 @@ Docs: [https://docs.nexmo.com/verify/api-reference/api-reference#control](https:
 ### Create an application
 
 ```python
-response = client.create_application(name='Example App', type='voice', answer_url=answer_url)
+response = client.create_application(name='Example App', type='voice', answer_url=answer_url, event_url=event_url)
 ```
 
 Docs: [https://docs.nexmo.com/tools/application-api/api-reference#create](https://docs.nexmo.com/tools/application-api/api-reference#create?utm_source=DEV_REL&utm_medium=github&utm_campaign=python-client-library)