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).