Related to #91

It's possible to emulate multiple xbox controllers over 1 usb device using the wireless receiver packets.
I tried to do this myself, and got some basic poc working here.
However, I did it with a rpi zero, which is easily able to support all the endpoints.

The wireless receiver supports 4 devices, each with 2 interfaces (one control, one for audio) which each have 2 endpoints (in/out).
With my poc I'm not fully able to emulate the receiver, instead I changed the interface protocol for controller input to that of the regular controller.

Maybe it'd also be possible to edit the config descriptor and then e.g., drop the audio interfaces as well. This way the ATmega32U4 might possibly be able to support 3 controllers. Seeing that this lib aims for that hardware.

I think it'd be awesome if this gets added, seeing that it could make some projects more compact using only 1 device.

Thoughts?