Add LED description

The programmable LED needs to be descibed in the docs:

It can be controlled with:

root@pureos:/# echo 200 > /sys/class/leds/LED\ 1/brightness

where 0 is "off", and any value between 1 and 255 is "on" with the default device tree. The LED is driven by a PWM shared with the haptic motor, so only one can be gradual at a time, decided by device tree.

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Eric about the 3 charge controller LEDs without a battery plugged in:

the two LEDs that were on are one that is on VBAT_REG (meaning VBAT_REG is likely being properly regulated), and PG# (Power Good). The third LED is attached to the charge controller's STAT pin, which would indicate whether or not a battery is being charged (can blink @ ~11Hz or be off if no battery is present, basically meaningless without a battery)

if you are powering from a battery but are not supplying VBUS, then you will just see the VBAT_REG LED on, the PG# and STAT ones will be off (unless you are supplying VBUS)

VBUS is USB.

for the LEDs, best thing to do is look at the schematic and charge controller's datasheet to know what it actually means