Deep Sleep
- API: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/sleep_modes.html
- Good tutorial about the subject: https://randomnerdtutorials.com/esp32-deep-sleep-arduino-ide-wake-up-sources/
- Explanations from Adafruit on the Huzzah board power management: https://learn.adafruit.com/adafruit-huzzah32-esp32-feather/power-management
