add TOC

Author: mamccrea

articles/stream-analytics/TOC.yml

@@ -42,6 +42,8 @@
       href: stream-analytics-documentdb-output.md
   - name: Window functions
     href: stream-analytics-window-functions.md
+  - name: Geospatial functions
+    href: stream-analytics-geospatial-functions.md
   - name: Compatibility level
     href: stream-analytics-compatibility-level.md
   - name: Common query patterns