Add example inventory and group_vars

ansible/group_vars/cluster/settings.yml.example

+# External ip address of the cluster.
+ip_address: "203.0.113.6"
+# Main domain name of the cluster services.
+domain: "example.com"
+# Email address of someone administering the cluster.
+admin_email: "admin@example.com"
+# Label of this deployment.
+release_name: "test"

ansible/inventory.yml.example

+all:
+  hosts:
+    oas-dev:
+      # Node to deploy to; can be a name or address.
+      ansible_host: "203.0.113.6"
+      # Ssh user to log in as.
+      ansible_user: "root"
+  children:
+    cluster:
+      hosts:
+        oas-dev
+    master:
+      hosts:
+        oas-dev
+    worker:
+      hosts:
+        oas-dev