Add Google Cloud K3s infrastructure support

- Add Terraform configuration for GCP instance and storage
- Add startup script for K3s installation and configuration
- Add pipeline scripts for deployment and management
- Add Forgejo deployment manifests and configuration

gcloud/tf/terraform.tfvars.example

@@ -0,0 +1,14 @@
+// Your GCP project name
+// it will be refererred as the project id
+// in Google Cloud
+// ----------------------------------
+project_name = "<your gpc project name>"
+
+// application name
+app_name = "your-projects-k3s-cluster"
+
+// where to deploy to
+// region
+region = "us-central1"
+zone   = "us-central1-a"
+