Make the tusb module functional for HID/CDC

[auxym]

Implement basic TinyUSB support:

• USB device stack API
• USB HID (keyboard/mouse/gamepad) device class API
• USB CDC (serial port) device class API

A small part of descriptor definition is wrapped, but most of it still has to be done in C. An example is provided that demonstrates HID and CDC functionality and descriptor config in C (taken from tinyusb examples).

Please review and ~nitpick~ provide constructive criticism on the tusb.nim exported API. API design is hard and now is the time to get it close to right. I tried to make it slightly higher level than the "raw" tinyusb API so it's less complex to use for library users, but still exposes most functionality (in a sane way). I also tried to model the interface types (UsbSerialInterface and UsbHidInterface) after the GPIO api.

Closes #38

[auxym]

Alright, pushed a few commits that:

• Add the static check for calling the callback templates at most once
• change the untyped param for string or openArray[uint8]
• Bump the nimble patch version

Let me know what you think about the remaining C stuff.