message: Modified alerts and reports docs for clarity
diff: @@ -33,6 +33,9 @@ Alerts and reports are disabled by default. To turn them on, you need to do some
  - You must install a headless browser, for taking screenshots of the charts and dashboards. Only Firefox and Chrome are currently supported.
  > If you choose Chrome, you must also change the value of `WEBDRIVER_TYPE` to `"chrome"` in your `superset_config.py`.
  +Note : All the components required (headless browser, redis, postgres db, celery worker and celery beat) are present in the docker image if you are following [Installing Superset Locally](https://superset.apache.org/docs/installation/installing-superset-using-docker-compose/).
  +All you need to do is add the required config (See `Detailed Config`). Set `ALERT_REPORTS_NOTIFICATION_DRY_RUN` to `False` in [superset config](https://github.com/apache/superset/blob/master/docker/pythonpath_dev/superset_config.py) to disable dry-run mode and start receiving email/slack notifications.
  +
  #### Slack integration
  To send alerts and reports to Slack channels, you need to create a new Slack Application on your workspace.
  