ios(guide): add instructions for building for App Store Upload

[GitToTheHub]

Platforms affected

• iOS

Motivation and Context

• Add section Building for App Store Upload, showing an example how to create an IPA for the App Store upload.
• Note, that --device has to be added to cordova build ios --release to create an IPA.
• Note, that packageType can be set by build.json and must not be set extra
• Generated-By: GPT-5.3-Codex

Description

Testing

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary