fix: change package manager to pnpm in CI

Author: davejsdev

.github/workflows/ci.yml

@@ -20,6 +20,10 @@ jobs:
         uses: actions/setup-node@v3
         with:
           node-version: '24.x'
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v2
+        with:
+          version: 8
       - name: Install dependencies
         run: pnpm ci
       - name: Run Linters