[skip ci] Add C++ SDK link

README.md

@@ -16,7 +16,7 @@ Milvus is the world's fastest similarity search engine for massive-scale feature
 
 For more detailed introduction of Milvus and its architecture, see [Milvus overview](https://www.milvus.io/docs/en/aboutmilvus/overview/).
 
-Milvus provides stable [Python](https://github.com/milvus-io/pymilvus), [Java](https://github.com/milvus-io/milvus-sdk-java) and C++ APIs. 
+Milvus provides stable [Python](https://github.com/milvus-io/pymilvus), [Java](https://github.com/milvus-io/milvus-sdk-java) and [C++](https://github.com/milvus-io/milvus/tree/master/core/src/sdk) APIs. 
 
 Keep up-to-date with newest releases and latest updates by reading Milvus [release notes](https://www.milvus.io/docs/en/release/v0.5.2/).