Update Documentation.md

Documentation.md

@@ -18,6 +18,7 @@ Being a private preview, Azure app has certain limitations as detailed below. We
 > [!NOTE]
 > * The app posts notifications for metric alerts. Support for 'activity log' and 'log alerts' will added soon.
 > * Alerts with multiple conditions or a single metric alert with multiple dimensions are not supported.
+> * This app supports [Common alert schema](https://docs.microsoft.com/en-us/azure/azure-monitor/platform/alerts-common-schema) notifications only.
 > * Need to add a point on user id in ADO. WIll have to frame accordingly.