Cache zalando images

[kogsox]

What is the problem you're trying to solve
Zalando hosts its images on registry.opensource.zalan.do/*, for their postgres distribution that is required by their operator

Describe the solution you'd like
being able to cache images from the Zalando registry

Additional context

[JXavierMSFT]

Hey @kogsox

We are looking into adding more upstreams to the feature. I've recorded your request as a new upstream to add. I'll update this thread once we make a decision.