利用pading-bottom实现宽高比例自适应

可以参考：
https://juejin.im/post/5b0784566fb9a07abd0e14ae#heading-0

还可以参考：
https://blog.csdn.net/TCF_JingFeng/article/details/80838903
https://blog.csdn.net/weixin_44151357/article/details/102501571
https://www.cnblogs.com/daisygogogo/p/9344727.html

https://blog.csdn.net/weixin_30752377/article/details/97398334?utm_medium=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.nonecase&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.nonecase

https://blog.csdn.net/weixin_34198453/article/details/88769760?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-1.nonecase&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-1.nonecase

https://www.cnblogs.com/yangmengsheng/p/8514005.html