Add a workflow to update test262 tests weekly (#12523)

* chore: draft update parser tests workflow

* Build babel parser

* chore: use Babel bot as git user name

* use babel-bot token

* refactor: use actions/github-script

* rename

scripts/parser-tests/get-test262-version.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+# Get the latest HEAD of tc39/test262
+# usage:
+# sh ./scripts/parser-tests/bump-test262-version.sh
+
+set -e
+export GIT_DIR=./build/test262/.git
+git fetch -q origin HEAD
+git rev-parse FETCH_HEAD