new top toc node

Author: diberry

articles/cognitive-services/LUIS/toc.yml

@@ -304,7 +304,9 @@
     href: reference-pattern-syntax.md
   - name: Sentiment
     href: luis-reference-prebuilt-sentiment.md
-  - name: Developer resources
+- name: Developer reference
+  items:
+  - name: Overview
     href: developer-reference-resource.md
     displayName: SDK, API, quickstart, REST, cli, powershell, azure, rm, resource manager, samples, package, module, tool, dispatch, bot
   - name: Azure CLI