Example project login state check failure

[maxism]

Hi and thanks for your work!

To test the possibility of using the package, I cloned the repository and tried to start it from the example folder. For this (as written in the instructions) I opened Xcode and check enabled "Sign In with Apple" capability for all build targets and changed signing account to my own.

The application started without problems, the signing in procedure works without problems, but when it comes to login state check, it fails. I think it might be connected with #7, cause i have the same error:

flutter: getCredentialState returned an error: The operation couldn’t be completed. (com.apple.AuthenticationServices.AuthorizationError error 1000.)

My flutter doctor output:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, v1.17.0-3.4.pre, on Mac OS X 10.15.4 19E287, locale en-RU)
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 11.4.1)
[!] Android Studio (not installed)
[✓] VS Code (version 1.45.0)
[✓] Connected device (1 available)