[Fix-4522] add use pnpm image (#4527)

Author: aiwenmo

.github/workflows/docs.yml

@@ -25,6 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+      - uses: pnpm/action-setup@v4
       - name: Build documentation
         run: |
           cd docs && pnpm install && pnpm run build