adding identifiers to TOC

Author: gregli-msft

powerapps-docs/maker/TOC.yml

@@ -563,6 +563,8 @@
             href: ./canvas-apps/functions/function-hashtags.md
           - name: Hour
             href: ./canvas-apps/functions/function-datetime-parts.md
+          - name: Identifiers
+            href: ./canvas-apps/functions/operators.md
           - name: If
             href: ./canvas-apps/functions/function-if.md
           - name: IfError