docs/library: Document new esp32.RMT features and fix wait_done.
docs/library: Document new esp32.RMT features and fix wait_done.

Add new API for specifying the idle level and TX carrier output level, and
new write_pulses modes of operation.  Also fix wait_done documentation
which was inverted and wrong about timing.

adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,bvernoux/micropython,bvernoux/micropython,adafruit/circuitpython,adafruit/circuitpython,bvernoux/micropython