optimize: 通过DS代理的请求，响应头添加 `DS-Proxy-Request`

(cherry picked from commit d6f550c694486913025e91c3bbd3a2d1e27bc04e)

packages/mitmproxy/src/lib/proxy/mitmproxy/createRequestHandler.js

@@ -128,6 +128,7 @@ module.exports = function createRequestHandler (createIntercepts, middlewares, e
           // log.debug('rOptions:', rOptions.hostname + rOptions.path, '\r\n', rOptions)
           // log.debug('agent:', rOptions.agent)
           // log.debug('agent.options:', rOptions.agent.options)
+          res.setHeader('DS-Proxy-Request', rOptions.hostname)
           proxyReq = (rOptions.protocol === 'https:' ? https : http).request(rOptions, (proxyRes) => {
             const cost = new Date() - start
             if (rOptions.protocol === 'https:') {