Create examples

[naporin0624]

• Create content comparing color-mix and alpha-blend in css
  • Prepare a sample of mix-color play
• Write that it is valid to use with react-native.
• Add Usage to README

[naporin0624]

react-native cannot use css and mix-color is not present. Therefore, alpha-blend is valid.

const Button = () => {
  const style = ({ pressed }: PressableStateCallbackType) => {
    return StyleSheet.flatten(StyleSheet.compose([styles.button, pressed ? styles.pressed : undefined]))
  }
  
  return (
    <Pressable style={style}>
      <Text>press here!</Text>
    </Pressable>
  )
}

const styles = StyleSheet.create({
  button: {
    backgroundColor: buttonColor,
  },
  pressed: {
    backgroundColor: alphaBlend(buttonColor, OVERLAY_COLOR)
  }
})