Guids: Add "How to start ST installation on real hardware"

Write a How-To Guide that focuses on the setting up a disk / USB drive / etc to run ST installation on (a certain) hardware. It assumes that you already have an ISO/UKI file and only explains what firmware(UEFI) and UEFI settings are needed, where to put and how to name the ST UKI/ISO in order to be loaded by the firmware.

(This is the How-To Guide part of #28 (closed) )