Rename docker-compose.yml to compose.yml

- Use modern Compose file naming convention
- Remove deprecated version specification
- Update command example to use 'docker compose'

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

compose.yml

@@ -0,0 +1,11 @@
+services:
+  security-lint:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: php-security-linter:latest
+    volumes:
+      # Mount the target directory as read-only
+      - ${TARGET_PATH:-.}:/target:ro
+    # Default command can be overridden
+    # Example: docker compose run --rm security-lint /target/app -s high