Add IO9 / VBAT_SENSE to lilygo-t8-s2-st7789

[skieast]

Added IO9 / VBAT_SENSE pin to lilygo_t8_s2_st7789 board
Tested with

import board
import analogio

vbat_voltage = analogio.AnalogIn(board.VBAT_SENSE)


def get_voltage(pin):
    return (pin.value * 3.3) / 65536 * 2


while True:
    battery_voltage = get_voltage(vbat_voltage)
    print("VBat voltage: {:.2f}".format(battery_voltage))
    time.sleep(1)
````

[tannewt]

Thanks for the PR! One request

[anecdata]

Addresses #5277

Requested change has been addressed.