HTTP Client Hints

简言之： 就是通过一种机制，让client告诉server自己有哪些特性，便于server能更好地为该client提供定制的服务

参考： https://imququ.com/post/http-client-hints.html

https://docs.imgix.com/tutorials/responsive-images-client-hints?_ga=1.267838798.110287679.1468903970