A rip-off python port of the following:
https://github.com/ciniml/WioTerminal_BackLight
LCD backlight pin (PC05) is not connected to any TC/TCC, but can be modulated by TC3 via EVSYS.
LCDBacklight.mpy
import LCDBacklight
LCDBacklight.init()
LCDBacklight.brightness(0.5)
# do-whatever-you-want
LCDBacklight.deinit()