fix: add DNS admin to Editor role (#146)

Resolves #145 by adding the DNS admin role to the Editor role.

Author: scotwells

config/assignable-organization-roles/roles/datum-cloud-editor.yaml

@@ -22,3 +22,5 @@ spec:
       namespace: milo-system
     - name: resourcemanager.miloapis.com-organization-viewer
       namespace: milo-system
+    - name: dns.networking.miloapis.com-dns-admin
+      namespace: milo-system