feat: improve rules_js parity

tests/js_compat_test/run_devserver.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+binary="$1"
+output="$("${binary}")"
+
+if [[ ${output} != "helper:payload-from-lib compat-mode devserver-mode" ]]; then
+  echo "unexpected output: ${output}" >&2
+  exit 1
+fi