Add Postal Code to the Credit Card Check Out Sample

[samizerouta]

I would like to have a sample credit card check out with a postal code field either by creating a new sample or adding the postal code to the existing one.

This is a case that we want to handle, I can create a PR if it's ok for you.

[MRDEANAT123]

Indeed

[newbein123]

Pls add postal codes