Provide a docs template for cards & document it

Provide a template in the docs to print out (like the onboarding cards). So that everyone can print an inlay for the birthday cards.

• A usable template is deployed to the docs
• It is documented how to use the template
• It is documented how and wehre the custom card can be found
• Document how the cards are created
• Document which material is needed for the cards (inlay & outer card)