Add install/setup instructions to README

[ohthehugemanatee]

Most of the issues on here seem to be from incorrect setup, and I'm struggling with similar basic questions. A step-by-step would be helpful, including:

• link to your custom klipper repo, explanation if it's required or not, and link to instructions to build and install that firmware.
• explanation of what to do with the config files. Just dump them all into the config directory? Rename the printer config? Do you have to add include statements for all the other files, or just prtouch.cfg? What do you need to add to the top of printer.cfg (mcu and virtual_sdcard sections)

thank you for your efforts to make this work!

[T9Air]

@ohthehugemanatee 1. link to custom repo. It is needed if you want to use the prtouch.cfg, which allows you to be able to set the z-offset automatically, like in Marlin. To add it to KIAUH see this website. Then build and run firmware from KIAUH as if installing a new version of KLIPPER that needs to be done from KIAUH.
2. Yes, you just put the config files in the config directory, if you want to include both prtouch.cfg if you want to use automatic z-offset, and if you want to use a filament sensor, you add in filament_sensor.cfg. They both go in printer.cfg. You do not need to add anything else to printer.cfg for it to work.