Implemented the real server

src/game_server/NetworkProtocol.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "../external/nlohmann/json.hpp"
+#include <string>
+
+namespace FRG {
+
+inline constexpr int kGameProtocolVersion = 1;
+
+std::string makeStateMessage(const nlohmann::json& state);
+bool parseStateMessage(
+	const std::string& message, nlohmann::json& state,
+	std::string& error);
+
+} // namespace FRG