[Feature Request] libnotify integration

Similar to #890, it would be great to integrate libnotify for more visible notifications when multitasking.

My typical dev setup: Ubuntu, runring Q inside of a hidden [Guake](https://guake.github.io/) terminal. It's hidden, so I don't see visual bells, nor do I have headphones on for audible bells. libnotify would dump notifications directly into the shared notification queue at the OS level.

I suppose there's a lot of overlap with #2867 though