Update README.md

cpp/README.md

@@ -8,6 +8,7 @@
 
 怎样添加provider 以支持gpu等，下面以cuda为例
 
+```
   OrtEnv* env;
   OrtInitialize(ORT_LOGGING_LEVEL_WARNING, "test", &env)
   OrtSessionOptions* session_option = OrtCreateSessionOptions();
@@ -17,4 +18,5 @@
   OrtReleaseObject(factory);
   OrtCreateSession(env, model_path, session_option, &session);
 
-`
+
+```