function useMergedStyles(theme, props, styleConfig, internalStyles) {
  const styleRef = useRef({})

  return useMemo(() => {
    const combinedStyles = combineStyles(theme, props, styleConfig, internalStyles)
    if (!isEqual(styleRef.current, combinedStyles)) {
      styleRef.current = combinedStyles
    }

    return styleRef.current
  }, [theme, props, styleConfig, internalStyles])
}
Combines a styleConfig object with internal styles based on the theme + style modifiers (props)
and returns a memoized style object
@returns {StyleConfig}