Prettification Notification

Prettification Notifications are disabled by default. To enable them, add a prettificationNotification entry with the Markdown text of the comment to your .github/prettifier.yml file. Here is an example:

prettification-notification: >
  Thanks for your contribution and welcome to this project! We format our source
  code using [Prettier](https://prettier.io). I have adjusted the formatting of
  this pull request for you.

  To stop seeing this message, please install Prettier on your machine and run
  `make format` to format your changes before submitting them.

Add this setting via a pull request that also contains some unformatted changes to see how the message would look like