Add support for Bluetooth

[freakboy3742]

What is the problem or limitation you are having?

Bluetooth is a common protocol for interacting with hardware devices. At present, Toga does not provide any mechanism for communicating with Bluetooth devices.

Describe the solution you'd like

Toga should provide an API for communicating with Bluetooth.

The exact shape of this API is an open question. It would presumably live in the app.hardware namespace.

Describe alternatives you've considered

It may be preferable to not support this in Toga, and instead use a third-party library.

Bleak is a Python library that has support for Bluetooth on desktop platforms and Android (although the Android support is Kivy specific).

BleekWare is a limited replacement for Bleak that is compatible with BeeWare's Android support.

Additional context

No response