AttributeSet attrs

참고 :
https://gun0912.tistory.com/38
https://stackoverflow.com/questions/5316686/what-is-attributeset-and-how-can-i-use-it
https://gogorchg.tistory.com/entry/Android-CustomView%EC%97%90-Attribute-%EB%A7%8C%EB%93%A4%EA%B8%B0