fix: update STACKS_DIR to use script directory as fallback

dclint.sh

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-STACKS_DIR="/srv/stacks"
+SCRIPT_DIR="$(dirname -- "$(readlink -f -- "${BASH_SOURCE[0]}")")"
+STACKS_DIR="${STACKS_DIR:-$SCRIPT_DIR}"
 docker_args=(--rm -v "$STACKS_DIR:/app")
 dclint_args=(. -r)