Feature: Added refreshToken and saveCredentials to auth0 hook

[StephenTANM]

Changes

Please describe both what is changing and why this is important. Include:

I've added refreshToken and saveCredentials to the auth0 hook for implementations requiring custom handling. For my use case at my professional job, we need to handle the refreshToken a certain way according to biometrics permissions and other factors.

References

Please include relevant links supporting this change such as a:

https://github.com/auth0/react-native-auth0/issues/625

Please note any links that are not publicly accessible.

Testing

Please describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. If this library has unit and/or integration testing, tests should be added for new functionality and existing tests should complete without errors.

• [x] This change adds unit test coverage
• [x] This change has been tested on the latest version of the platform/language or why not

Checklist

• [x] I have read the Auth0 general contribution guidelines
• [x] All existing and new tests complete without errors
• [ ] All active GitHub checks have passed