[DevKit] provide a HOWTO showing on how to extend a receipt with customer information

[turtletramp]

Customer Stefan Gurszky asked how they can add customer information to a receipt issued (company name, UID, Address) mainly needed for Germany.

GOAL: Create a HOWTO that shows
a) how to issue receipts (variant 1 - manually created (if this is even possible), variant 2 - when it comes from the sign call)
b) how to add customer information