fix: type CreateStyledComponent to accept string and object

[FourwingsY]

fixes #188

The code below now does not show type errors.

const Colors = {
  text: '#000',
  highlight: '#25f'
}
const typo_body = {
  fontSize: 14,
  fontWeight: 500
}

const ButtonWithMixedInterpolation = styled.button`
  ${typo_body};
  color: ${Colors.highlight};
`;