Add Card Fields to README

[buzzamus]

Summary of changes

• This adds a Card Fields example to the README file like our other features

AI Usage

Which AI Agent Was Used?

• Copilot
• Claude
• Other (Type Name Here)

How was AI used?
Used Claude to create the example for me and proofread

Estimated AI Code Contribution

• less than 30%
• 30 - 60%
• 60 - 100%

Checklist

• Added a changelog entry
• Tested and confirmed payment flows affected by this change are functioning as expected

Authors

List GitHub usernames for everyone who contributed to this pull request.

• @buzzamus

[buzzamus]

@noguier FYI in case there is anything here you think should be changed to match Android at all

[noguier]

Do we want to mention that if needed merchants can provide additional info to the CardFields, such as postal code, name, etc.?

[buzzamus]

Do we want to mention that if needed merchants can provide additional info to the CardFields, such as postal code, name, etc.?

That is a good idea although most of the README examples are fairly basic and I am assuming that is to avoid too much detail and making the README overly long. I think that is definitely a good callout we should put an example for in the dev docs when we write them

[agedd]

🚀