Add notification after server restart

[christopher-francisco]

The notification is done with node-notifier.

[ghost]

Hello @chris-fa. Thanks for your PR.

It looks like a new addition instead of a feature that is necessary for the package. So could you disable the notifications by default and implement enabling them via CLI options?

I remember the Laravel Elixir also showed such a notification after building the code, which irritated me very much. That's why I think showing system notifications by default can be annoying for other developers 😄

Thanks!

[STRML]

This can be done now with --before-restart:

babel-watch --before-restart="echo 'restarted!' | terminal-notifier" app.js