add: Response 添加一个json方法，便捷的回复json格式数据；request添加一个context成员，便于在处理链的各个环节共享数据

test_minweb_server_library.cpp

@@ -45,9 +45,6 @@ int main () {
     service.homePage = "index.html";
     service.baseUrl = "/MIN/Web/test";
 
-    std::cout << getMINHttpMethodEnumFromStr("GET") << std::endl;
-    std::cout << getMINHttpStatusEnumFromStr("Continue") << std::endl;
-
     service.GET("/getUserInfo", [](std::shared_ptr<MINWebRequest> &request,
                                    std::shared_ptr<MINWebResponse> &response) {
         nlohmann::json result = {