chore(ci): add the sh script to prevent Vercel deploying from forks (#8986)

Author: KSDaemon

.github/actions/vercel-deploy-check.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+
+if [ "$VERCEL_GIT_REPO_OWNER" != "cube-js" ]; then
+  echo "Skipping deploy for PR from a fork."
+  exit 0
+fi
+
+# In other case return the usual git diff for a root folder
+git diff HEAD^ HEAD --quiet ./