Use a more helpful variable description

Many thanks to @qvallance for this tip!

variables.tf

@@ -66,9 +66,20 @@ variable "node_version" {
 }
 
 variable "master_authorized_networks_config" {
-  description = "The desired configuration options for master authorized networks. Omit the nested cidr_blocks attribute to disallow external access (except the cluster node IPs, which GKE automatically whitelists)."
   type        = "list"
-  default     = []
+  description = <<EOF
+  The desired configuration options for master authorized networks. Omit the nested cidr_blocks attribute to disallow external access (except the cluster node IPs, which GKE automatically whitelists)
+
+  ### example format ###
+  default = [{
+    cidr_blocks = [{
+      cidr_block   = "10.0.0.0/8"
+      display_name = "example_network"
+    }],
+  }]
+
+  EOF
+  default = []
 }
 
 variable "horizontal_pod_autoscaling" {