esp8266/README: comment on the specific binary SDK used
esp8266/README: comment on the specific binary SDK used

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