Add new alerting document type to ED

otc_metadata/data/documents/ed-alerting.yaml

@@ -0,0 +1,11 @@
+---
+link: /enterprise-dashboard/alerting/
+rst_location: doc/alerting/source
+service_type: ed
+title: Alerting
+type: alerting
+cloud_environments:
+  - name: eu_de
+    visibility: public
+    pdf_visibility: public
+    pdf_enabled: true