Fix example in readme.

README.adoc

@@ -17,6 +17,8 @@ the other wrappers are either incomplete or unmaintained as well.
 
 namespace cw = curl_wrapper;
 
+int main()
+{
     cw::CURLWrapper curl;
     const auto answer{curl.make_http_request(cw::http_method::GET,
                                              "http://example.com/")};
@@ -24,6 +26,7 @@ if (answer)
     {
         std::cout << answer;
     }
+}
 --------------------------------------------------------------------------------
 
 == Use with CMake