Create documentation regarding shipping a repaired product

[cristinastefan90]

Create a step by step documentation on how to ship back a product which was send them back for repair.

[metas-Kay]

Please see these docs here:

• EN: How to process returned products in need of repair (warranty cases)
• DE: Re­pa­ra­tur­be­dürf­tige Retouren bearbeiten (Garantiefälle)