Add a Brightness Feature

Having just started using my Core Steel 2, when I went outside in the sun and even in the shade, it was barely visible at all. Perhaps adding a function that allows you to adjust the brightness, would be helpful to many. If you can't make it a variable brightness, then a hign, mediim and low level might be possible. Thanks for being receptive to the suggestion.

Merged into "Core: Increase brightness of display" #36