Adds an instant LED duration preference that only keeps the LED lit while the LIGHT button remains held down. Matches the behavior of the original watch. Reviewed-by: Matheus Afonso Martins Moreira <matheus@matheusmoreira.com> Tested-on-hardware-by: Wesley Aptekar-Cassels <me@wesleyac.com> Tested-on-hardware-by: 814d3 (GitHub) GitHub-Pull-Request: https://github.com/joeycastillo/Sensor-Watch/pull/293