Consider brightness differentiation between screens on the combined brightness slider of dual screen devices #202

Currently the combined brightness slider just sets the same brightness to both screens.

The Thor's top screen is actually a bit brighter than the top screen, so when setting both screens to 50% the top one always looks a bit brighter than the bottom one.

Ayn adjusted their combined brightness slider a bit after release so it sets both screens to a similar brightness level instead of just matching the percentage.

A similar adjustment may also benefit Armada.