Add remaining fields for signing up a user

[travisobregon]

Changes

This allows passing all available parameters to the signup endpoint.

References

This resolves #352

Testing

You can pass additional parameters to the createUser method, such as name

• [ ] 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