mention netron visualizer

README.md

@@ -47,6 +47,8 @@ ncnn 是一个为手机端极致优化的高性能神经网络前向计算框架
 
 **[ncnn 组件使用指北 alexnet](https://github.com/Tencent/ncnn/wiki/ncnn-%E7%BB%84%E4%BB%B6%E4%BD%BF%E7%94%A8%E6%8C%87%E5%8C%97-alexnet) 附带详细步骤，新人强烈推荐 :)**
 
+**[use netron for ncnn model visualization](https://lutzroeder.github.io/netron/)**
+
 [ncnn low-level operation api](https://github.com/Tencent/ncnn/wiki/low-level-operation-api)
 
 [ncnn param and model file spec](https://github.com/Tencent/ncnn/wiki/param-and-model-file-structure)