Notification component

### The InAppNotification control offers the ability to show local notifications in your application.

![inappnotification](https://user-images.githubusercontent.com/4184558/67688439-1d197c00-f99a-11e9-8a03-426105fcaa05.gif)

More details can be found in the [Community toolkit documentation](https://docs.microsoft.com/en-us/windows/communitytoolkit/controls/inappnotification)