add reference card to landing

Author: vhorne

articles/firewall-manager/index.yml

@@ -66,3 +66,16 @@ landingContent:
         links:
          - text: Azure network security
            url: ../networking/security/index.yml
+
+# Card
+  - title: Reference
+    linkLists:
+      - linkListType: reference
+        links:
+          - text: Azure CLI
+            url: /cli/azure/network/firewall
+          - text: Azure PowerShell
+            url: /powershell/module/az.network/new-azfirewall
+          - text: REST
+            url: /rest/api/firewall
+