Refactoring CSS
1 : https://www.smashingmagazine.com/2021/07/refactoring-css-introduction-part1/
2 : https://www.smashingmagazine.com/2021/08/refactoring-css-strategy-regression-testing-maintenance-part2/
CSS파일은 200KB 미만의 크기를 가지는게 적당함
https://stackoverflow.com/questions/41319026/optimize-css-file-size-too-big