message: Fix masterVersion missing import
  Add dbUsername config to the readme
diff: import * as gcp from "@pulumi/gcp";
  import * as k8s from "@pulumi/kubernetes";
  import * as pulumi from "@pulumi/pulumi";
  -import { clusterNodeCount, clusterNodeMachineType, clusterPassword, clusterUsername } from "./config";
  +import { clusterNodeCount, clusterNodeMachineType, clusterPassword, clusterUsername, masterVersion } from "./config";
  // Create the GKE cluster and export it.
  export const cluster = new gcp.container.Cluster("gke-cluster", {
  