Update toc.yml

Author: Juliako

articles/media-services/video-indexer/toc.yml

@@ -112,6 +112,8 @@
     href: https://gallery.technet.microsoft.com/Overview-of-Azure-c1be3942 
   - name: Release notes
     href: release-notes.md
+  - name: Stack Overflow
+    href: https://stackoverflow.com/search?q=video-indexer
   - name: User voice
     href: https://cognitive.uservoice.com/forums/598144-video-indexer
   - name: Blogs