Add example of using prelaunch script

examples/prelanch-script/docker-compose.yaml

@@ -0,0 +1,7 @@
+services:
+  busybox:
+    image: busybox:latest
+    command: sh -c "cat /etc/motd"
+    volumes:
+      - /tapp/motd:/etc/motd
+    restart: no

examples/prelanch-script/prelanch.sh

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+# This is an example of how to write a pre-launch script of DStack App Compose.
+
+# The script is run in /tapp directory. The app-compose.json file is in the same directory.
+
+set -e
+
+# We fully handle the docker compose logic in this script.
+echo "Extracting docker compose file"
+jq -j '.docker_compose_file' app-compose.json >docker-compose.yaml
+echo "Removing orphans"
+tdxctl remove-orphans -f docker-compose.yaml || true
+echo "Restarting docker"
+chmod +x /usr/bin/containerd-shim-runc-v2
+systemctl restart docker
+
+# Use a container to setup the environment
+echo "Setting up the environment"
+tdxctl notify-host -e "boot.progress" -d "setting up the environment" || true
+docker run \
+    --rm \
+    --name dstack-app-setup \
+    -v /tapp:/tapp \
+    -w /tapp \
+    -v /var/run/docker.sock:/var/run/docker.sock \
+    curlimages/curl:latest \
+    -s https://raw.githubusercontent.com/Dstack-TEE/meta-dstack/refs/heads/main/meta-dstack/recipes-core/base-files/files/motd -o /tapp/motd
+
+echo "Starting containers"
+tdxctl notify-host -e "boot.progress" -d "starting containers" || true
+if ! docker compose up -d; then
+    tdxctl notify-host -e "boot.error" -d "failed to start containers"
+    exit 1
+fi
+
+# Use exit to skip the original docker compose handling
+exit 0