Brightness control workaround

[ertdfgcvb]

User @mayankk2308 pointed out in #1 that there is an app called "Brightness Slider" for macOS which is free and can be found on the App Store.
This information is valuable as it's the only workaround I found to get back brightness adjustment for the laptop display.
Maybe this issue could stay open or these informations could be integrated in the readme.

Notes:

• make sure that the "Brightness Slider" app is not running during patching and first reboot (after reboot the brightness set itself to minimum)
• set the brightness to maximum before patching and first reboot as "Brightness Slider" won't be able to set the brightness above the last value set.

My system:
15" Retina MacBook (mid 2012), AMD RX 580