HTTP 请求的头部信息。类型为数组，所有 key 均为小写。
Swoole\Http\Request->header: array
示例
echo $request->header['user-agent']; echo $request->header['host']; echo $request->header['accept-language'];
可以获取的部分常用header
accept => text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9 accept-encoding => gzip, deflate accept-language => zh-CN,zh;q=0.9 cache-control => no-cache connection => keep-alive cookie => host => 192.168.195.129:9601 pragma => no-cache referer => sec-ch-ua => sec-ch-ua-mobile => sec-fetch-dest => sec-fetch-mode => sec-fetch-site => sec-fetch-user => upgrade-insecure-requests => 1 user-agent => Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.198 Safari/537.36
http的header相关资料
https://developer.mozilla.org/zh-CN/docs/Web/HTTP/Headers
https://tools.ietf.org/html/rfc4229
