Add Notification support for sending alerts.

[poush]

Instead of using alert() for any errors, we should rely on something better like the sliding notifications of macOS.

[poush]

On Windows 10, a shortcut to your app with an Application User Model ID must be installed to the Start Menu.
On Windows 8.1 and Windows 8, a shortcut to your app with an Application User Model ID must be installed to the Start screen. Note, however, that it does not need to be pinned to the Start screen.
On Windows 7, notifications work via a custom implementation which visually resembles the native one on newer systems.