Add a "Audio Stream" to include BT Mono

[IvanRaide]

As an example, look at the playstore app BTMono. This app is able to take all audio and ship it to BT Mono for playback on mono bluetooth headsets (often found in cars, (like mine)).
The problem with running BTMono is that its very simple, on all the time, or off. If in a car it interfers with regular audio since the car things its always in a phone call. But if VoiceNotifier turn on BTmono functionality, only on a speech notification, and then turned it off, it would be the ideal situation.