[📚] cloud_firestore docs should mention the workaround for faster macOS builds

[nilsreichardt]

When adding this line to your macos/Podfile, you are getting faster builds:

pod 'FirebaseFirestore', :git => 'https://github.com/invertase/firestore-ios-sdk-frameworks.git', :tag => "#{firebase_sdk_version}"

See #3185 for more details.

The example for cloud_firestore is also using the workaround:

flutterfire/packages/cloud_firestore/cloud_firestore/example/macos/Podfile

Line 53 in 641ece1

pod 'FirebaseFirestore', :git => 'https://github.com/invertase/firestore-ios-sdk-frameworks.git', :tag => "#{firebase_sdk_version}"

It would be helpful for new customers to mention this workaround in the docs.

[Jonas-Sander]

See also #7467

[darshankawar]

I think the linked issue will also address this issue, so its better to track it in #7467. The same has been acknowledge that the document can be updated to reflect the usage.

Closing this as duplicate.