update default prelaunch script for Phala Cloud

Author: Leechael

phala-cloud-prelaunch-script/README.md

@@ -0,0 +1,29 @@
+# Default Pre-launch script of Phala Cloud
+
+## Overview
+
+This pre-launch script for Phala Cloud handles:
+
+- Pull private images from Docker Hub
+- Pull private images from AWS ECR  
+- Remove unused images and containers from local disk
+- Expose App ID via `DSTACK_APP_ID` environment variable
+
+## Private registry support
+
+### Docker Hub Authentication
+
+Set these encrypted environment variables:
+
+- `DSTACK_DOCKER_USERNAME` - Your Docker Hub username
+- `DSTACK_DOCKER_PASSWORD` - Your Docker Hub password or access token
+
+### AWS ECR Authentication
+
+Set these encrypted environment variables:
+
+- `DSTACK_AWS_ACCESS_KEY_ID` - Your AWS access key ID
+- `DSTACK_AWS_SECRET_ACCESS_KEY` - Your AWS secret access key
+- `DSTACK_AWS_REGION` - AWS region for your ECR repository
+- `DSTACK_AWS_ECR_REGISTRY` - Your AWS ECR registry URL
+- `DSTACK_AWS_SESSION_TOKEN` - Only needed for temporary AWS credentials