新增于: v7.7.0
如果 name 标识的标头当前设置在传出标头中，则返回 true。标头名称匹配不区分大小写。
¥Returns true if the header identified by name is currently set in the
outgoing headers. The header name matching is case-insensitive.
const hasContentType = response.hasHeader('content-type');