Adafruit-circuitpython-hid

1. Added `ConsumerControl` and `ConsumerControlCode` to send multimedia control requests, such as volume up/down, play/pause, etc. Many keyboards have these keys. Supported only in CircuitPython 3.0 and up.

2. Added the convenience method `Keyboard.send(...)`, which combines `Keyboard.press(...)` and `Keyboard.release_all()`.

3. When `main.py` starts, the host may not yet have configured the HID devices. Wait for an extra second if necessary to ensure the host is ready (see issue 13).

Thanks to mrmcwethy for the great work!

Fixes issue 6. Some Keycodes were missing from the published documentation due to a sphinx configuration issue. Keycode.SPACE is added as an alias for Keycode.SPACEBAR.

Thanks to dhalbert this library has been greatly improved. It now features a separate [`Keycode`](https://circuitpython.readthedocs.io/projects/hid/en/latest/keycode.html) class along with improvements to the [`Mouse`](https://circuitpython.readthedocs.io/projects/hid/en/latest/mouse.html) class.

Contains basic HID related constants.