Notification indicators for Electron app

[haadcode]

The Electron apps' dock icon should display a notification indicator when new messages or highlights appear and the app is unfocused.

These can be dig out from the UI's internal highlight and mentions system and passed via Electron's IPC to the app's main process. Electron itself has a built-in support and functionality to display the icon in the dock.

[dignifiedquire]

On this note, native notifications for new messages would also be nice. I've used https://www.npmjs.com/package/node-notifier for this with great success