add readme

Signed-off-by: Jason Hall <jason@chainguard.dev>

container-vm/README.md

@@ -0,0 +1,39 @@
+# container-vm
+
+Terraform module that creates a GCE instance template running Docker containers on Container-Optimized OS, managed via cloud-init and systemd.
+
+This is intended to simulate and replace the [deprecated container startup agent](https://docs.cloud.google.com/compute/docs/containers/migrate-containers) using `cloud-init`.
+
+## Features
+
+- Runs one or more containers with systemd service management
+- Supports Container-Optimized OS (COS) with pre-installed Docker
+- Artifact Registry authentication via docker-credential-gcr
+- Cloud Logging integration with gcplogs driver
+- Shielded VM with secure boot enabled
+- Requires digest-pinned container images for security
+
+## Usage
+
+```hcl
+module "container_vm" {
+  source = "./container-vm"
+
+  project_id             = "my-project"
+  region                 = "us-east4"
+  network                = "default"
+  subnetwork             = "default"
+  service_account_email  = "my-sa@my-project.iam.gserviceaccount.com"
+
+  containers = {
+    web = {
+      image = "us-east4-docker.pkg.dev/my-project/my-repo/app@sha256:abc123..."
+      ports = ["8080:8080"]
+      env = [{
+        name  = "PORT"
+        value = "8080"
+      }]
+    }
+  }
+}
+```