fix: add pnpm installation step to workflow

Author: d-oit

.github/workflows/reusable-hugo-workflow.yml

@@ -24,6 +24,12 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
+       - name: Install pnpm
+         uses: pnpm/action-setup@v4
+         with:
+           version: latest
+
+       - name: Set up Node.js
       - name: Set up Node.js
         uses: actions/setup-node@v4
         with: