Replace drop-shadow with box-shadow

INFO

This document represents an architecture decision record (ADR) and has been mirrored from the ADR section in our Shopware 6 repository. You can find the original version here

Context

Safari has drastic performance issues with drop-shadow.

Decision

Changing it to box-shadow solves all the performance issues.

Consequences

The design and optic of the drop-shadow is slightly different. It is not as perfect as before. But it looks almost the same and is much faster.