Fix documentation workflow to setup pnpm

.github/workflows/docs.yml

@@ -9,6 +9,10 @@ jobs:
         steps:
             - name: Checkout repository
               uses: actions/checkout@v4
+            - name: Setup pnpm
+              uses: pnpm/action-setup@v4
+              with:
+                version: latest
             - run: cd docs/
             - name: Install dependencies
               run: pnpm install