added bgp communities portal article

Author: duongau

articles/expressroute/TOC.yml

@@ -167,7 +167,11 @@
       - name: Azure PowerShell
         href: expressroute-howto-reset-peering.md
     - name: Configure BGP community value for VNet
-      href: how-to-configure-custom-bgp-communities.md
+      items:
+      - name: Azure portal
+        href: how-to-configure-custom-bgp-communities-portal.md
+      - name: Azure PowerShell
+        href: how-to-configure-custom-bgp-communities.md
     - name: Move from public peering to Microsoft peering
       href: how-to-move-peering.md
   - name: Encrypt traffic over circuits