Map your hot keys to increase or decrease the screen brightness in i3 wm
sudo pacman -S brightnessctl
sudo apt-get install brightnessctl
sudo dnf install brightnessctl
bindsym XF86MonBrightnessUp exec --no-startup-id brightnessctl set +5%
bindsym XF86MonBrightnessDown exec --no-startup-id brightnessctl set 5%-