message: Improve doc : Add get broadcast status section
diff: @@ -649,7 +649,7 @@ controller.api.handover.request_thread_control('<RECIPIENT_PSID>', 'String to pa
  });
  ```
  -### Cancelling a Scheduled Broadcast
  +### Cancel a Scheduled Broadcast
  - To cancel a scheduled broadcast :
  ```javascript
  @@ -658,6 +658,14 @@ controller.api.handover.cancel_scheduled_broadcast('<BROADCAST_ID>', function (r
  });
  ```
  +### Get a Broadcast Status
  +
  +- To get a broadcast status :
  +```javascript
  +controller.api.handover.get_broadcast_status('<BROADCAST_ID>', ['scheduled_time', 'status'], function (result) {
  +
  +});
  +```
  ## Messaging type
  