Add benchmark tool

benchmark/cpp-httplib/main.cpp

@@ -0,0 +1,12 @@
+#include "httplib.h"
+using namespace httplib;
+
+int main() {
+  Server svr;
+
+  svr.Get("/", [](const Request &, Response &res) {
+    res.set_content("Hello World!", "text/plain");
+  });
+
+  svr.listen("0.0.0.0", 8080);
+}