add '--dbg-server' command-line argument & add debugging server draft

src/devtools/DebuggingServer.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <memory>
+#include <string>
+
+namespace network {
+    class Server;
+    class Connection;
+}
+
+class Engine;
+
+namespace devtools {
+    class DebuggingServer {
+    public:
+        DebuggingServer(Engine& engine, const std::string& serverString);
+        ~DebuggingServer();
+
+        bool update();
+
+        void setClient(network::Connection& client) {
+            this->client = &client;
+        }
+    private:
+        Engine& engine;
+        network::Server& server;
+        network::Connection* client;
+    };
+}