Add benchmark tool

benchmark/crow/main.cpp

@@ -0,0 +1,17 @@
+#include "crow_all.h"
+
+class CustomLogger : public crow::ILogHandler {
+public:
+  void log(std::string, crow::LogLevel) {}
+};
+
+int main() {
+  CustomLogger logger;
+  crow::logger::setHandler(&logger);
+
+  crow::SimpleApp app;
+
+  CROW_ROUTE(app, "/")([]() { return "Hello world!"; });
+
+  app.port(8080).multithreaded().run();
+}