Update index

Author: maud-lv

articles/managed-grafana/index.yml

@@ -39,6 +39,8 @@ landingContent:
             url: how-to-enable-zone-redundancy.md
           - text: Set up authentication and permissions
             url: how-to-authentication-permissions.md
+          - text: Create a dashboard
+            url: create-grafana-dashboard.md
   - title: Manage Azure Managed Grafana
     linkLists:
       - linkListType: how-to-guide