css3 video背景相关
设置视频背景透明
https://www.zhangxinxu.com/wordpress/2019/05/mp4-video-background-transparent/
https://www.zhangxinxu.com/wordpress/2015/05/css3-mix-blend-mode-background-blend-mode/
video {
mix-blend-mode: screen;
}
poster布满视频画面
video {
object-fit: cover;
}
可取值：fill、contain、cover
