custom sentiment link

Author: aahill

articles/ai-services/language-service/sentiment-opinion-mining/overview.md

@@ -82,4 +82,6 @@ An AI system includes not only the technology, but also the people who use it, t
 
 There are two ways to get started using the entity linking feature:
 * [Language Studio](../language-studio.md), which is a web-based platform that enables you to try several Language service features without needing to write code.
-* The [quickstart article](quickstart.md) for instructions on making requests to the service using the REST API and client library SDK.  
+* The quickstart articles for instructions on making requests to the service using the REST API and client library SDK (prebuilt sentiment analysis model only).
+    * [Use the prebuilt model](./quickstart.md)
+    * [Create a custom model](./custom/quickstart.md)