head中添加<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
https://getbootstrap.com/docs/4.0/getting-started/introduction/#css
Bootstrap 手机屏幕自适应的响应式布局开关
原文：https://www.cnblogs.com/xfbx/p/9344690.html
