Fix postBuild shebang; install Playwright at build

postBuild

@@ -1,8 +1,7 @@
-#!/usr/bin/envset -euxo pipefail
-
+#!/usr/bin/env bash
 set -euxo pipefail
 
 python3 -m pip install -U pip
 pip install -r requirements.txt
 python3 -m playwright install --with-deps chromium
-
+python3 -m playwright --version || true