Add support secret manager csi addon in beta (#10841) (#18303)

[upstream:3fc405dc19dd59b313710b2d8cd95ac57c109329]

Signed-off-by: Modular Magician <magic-modules@google.com>

Author: modular-magician

website/docs/r/container_cluster.html.markdown

@@ -292,6 +292,10 @@ region are guaranteed to support the same version.
     [PodSecurityPolicy](https://cloud.google.com/kubernetes-engine/docs/how-to/pod-security-policies) feature.
     Structure is [documented below](#nested_pod_security_policy_config).
 
+* `secret_manager_config` - (Optional, [Beta](https://terraform.io/docs/providers/google/guides/provider_versions.html)) Configuration for the
+    [SecretManagerConfig](https://cloud.google.com/secret-manager/docs/secret-manager-managed-csi-component) feature.
+    Structure is [documented below](#nested_secret_manager_config).
+
 * `authenticator_groups_config` - (Optional) Configuration for the
     [Google Groups for GKE](https://cloud.google.com/kubernetes-engine/docs/how-to/role-based-access-control#groups-setup-gsuite) feature.
     Structure is [documented below](#nested_authenticator_groups_config).
@@ -1106,6 +1110,10 @@ notification_config {
 * `enabled` (Required) - Enable the PodSecurityPolicy controller for this cluster.
     If enabled, pods must be valid under a PodSecurityPolicy to be created.
 
+<a name="nested_secret_manager_config"></a>The `secret_manager_config` block supports:
+
+* `enabled` (Required) - Enable the Secret Manager add-on for this cluster.
+
 <a name="nested_private_cluster_config"></a>The `private_cluster_config` block supports:
 
 * `enable_private_nodes` (Optional) - Enables the private cluster feature,