form is not re-rendered when using setValue to update a field that was manually registered

Describe the bug When registering fields manually, the form does not re-render after calling setValue.

To Reproduce

const MyForm = () => {
  const { register, unregister, getValues, setValue } = useForm({
    defaultValues: { email: '' }
  });

  useEffect(() => {
    register({ name: 'email' });
    return () => unregister({ name: 'email' });
  }, [register, unregister]);

  /* getValues does not work because setValue does not trigger a re-render */
  const values = getValues();

  const onChange = e => setValue(e.target.name, e.target.value, true);

  return <input type="text" name="email" value={values.email} onChange={onChange} />;
};

Expected behavior Explicitly calling setValue should trigger a re-render

The usual use-case would be to simply pass register into the input’s ref. However, manually registering fields is still required for components that don’t expose a ref prop. The above code snippet is just a contrived example to show that manually registering a field does not work as intended.