Add backlight dimmer option

This is based on n5dim by @mzhou  https://github.com/mzhou/n5dim

Signed-off-by: flar2 <asegaert@gmail.com>
More gradual levels for backlight dimmer mod (based on @mzhou module)

Signed-off-by: flar2 <asegaert@gmail.com>
Backlight dimmer mod: more gradual transitions

Signed-off-by: flar2 <asegaert@gmail.com>