feat: allow no timeout

Changes

Support for no timeout when fetching, this will allow people to use their own timeout/retry logic.

References

There has been multiple issues reported related to the timeout feature #792 and https://github.com/auth0/react-native-auth0/issues/514#issuecomment-1478806912

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.

• [ ] 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
• [ ] All existing and new tests complete without errors
• [ ] All active GitHub checks have passed

Default timeout is 10000 ms. and can be customised with Auth0Options. Closing this PR as this is already present.