README.md: kiauh not installed

[RobbyBer]

Hello,
maybe it will be nice, if you make a more explicit hint that kiauh is not installed on a default MainsailOS.

In "Step 1 - Setting up the Raspberry Pi" is the Text:
"(optional) If you want to use fluidd instead of Mainsail navigate to the kiauh directory: cd ../kiauh"
Maybe you can insert a line before with sometink linke that: (optional) Install kiauth Documentation at: https://github.com/th33xitus/kiauh