modified docusaurus admonitions in notification-api.md and transaction-error-in-checkout.md files.

docs/content/how-to/notification-api.md

@@ -77,6 +77,7 @@ class MyService extends NotificationService {
 
 export default MyService;
 ```
+
 :::note 
 
  A notification service must have a static property called `identifier` this is used to determine which classes are called when subscribing to different events. In this case the service identifier is `my-service` so to subscribe to notifications you must use: