Add validation of realm client and id

roles/keycloak_realm/README.md

@@ -71,6 +71,8 @@ Refer to [docs](https://docs.ansible.com/ansible/latest/collections/community/ge
 
 ```yaml
     - name: <name of the client>
+      id: <id of the client>
+      client_id: <id of the client>
       roles: <keycloak_client_default_roles>
       realm: <name of the realm that contains the client>
       public_client: <true for public, false for confidential>
@@ -78,6 +80,9 @@ Refer to [docs](https://docs.ansible.com/ansible/latest/collections/community/ge
       users: <keycloak_client_users>
 ```
 
+`name` and either `id` or `client_id` are required.
+
+
 * `keycloak_client_users`, a list of:
 
 ```yaml