[chore] add Vercel preview for PRs

.github/workflows/preview.yml

@@ -0,0 +1,21 @@
+name: Vercel
+env:
+  VERCEL_ORG_ID: ${{ secrets.VERCEL_ORG_ID }}
+  VERCEL_PROJECT_ID: ${{ secrets.VERCEL_PROJECT_ID }}
+on:
+  pull_request_target:
+    types: [labeled]
+jobs:
+  preview:
+    runs-on: ubuntu-latest
+    environment:
+      name: preview
+      url: ${{ steps.deploy.outputs.url }}
+    if: contains(github.event.pull_request.labels.*.name, 'safe to preview')
+    steps:
+      - uses: actions/checkout@v3
+      - run: npm install --global vercel@latest
+      - run: vercel pull --yes --environment=preview --token=${{ secrets.VERCEL_TOKEN }}
+      - run: vercel build --token=${{ secrets.VERCEL_TOKEN }}
+      - id: deploy
+        run: echo "::set-output name=url::$(vercel deploy --prebuilt --token=${{ secrets.VERCEL_TOKEN }})"