Add new error type to AuthenticationError

[lordzsolt]

• [X] All new/changed/fixed functionality is covered by tests (or N/A)
• [X] I have added documentation for all new/changed functionality (or N/A)

📋 Changes

This PR adds new error types to AuthenticationError to match those in Auth0.Android:

• isInvalidRefreshToken

📎 References

• 819

• https://github.com/auth0/Auth0.Android/blob/148df396c5706579b99bb7a1d26e00ea65a93753/auth0/src/main/java/com/auth0/android/authentication/AuthenticationException.kt#L204C16-L204C37

🎯 Testing

Test was added according to existing test specs.

[Widcket]

This is now out in v2.6.0.