fix: setup pnpm

Author: SamVerschueren

.github/workflows/ci.yaml

@@ -41,6 +41,10 @@ jobs:
     name: Docs
     runs-on: ubuntu-latest
     steps:
+      - name: Setup
+        uses: pnpm/action-setup@v4
+        with:
+          version: 8
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install dependencies