스트랩 col 중심 콘텐츠
<div class="row">
<div class="col-4 d-flex justify-content-center text-center">
// for image and text
</div>
</div>
alighn 오른쪽 부트스트랩 4
<div class="float-left">Float left on all viewport sizes</div><br>
<div class="float-right">Float right on all viewport sizes</div><br>
<div class="float-none">Don't float on all viewport sizes</div>
bootstrap justify-content-center for md
<div class="row justify-content-md-center"></div>
부트스트랩을 정당화 콘텐츠 센터 md
<div class="row justify-content-md-center"></div>
부트 스트랩 정당화-lg 용 콘텐츠 센터
<div class="row justify-content-lg-center"><div>