fix: make docs workflow use pnpm

.github/workflows/docs.yaml

@@ -41,13 +41,12 @@ jobs:
       - name: Build
         uses: actions/setup-node@v4
         with:
-          node-version: 16.x
-          cache: 'npm'
-      - run: npm ci
-      - run: npm run build # set up 'build' script in your package.json
+          node-version: 20.x
+          cache: 'pnpm'
+      - run: pnpm run build # set up 'build' script in your package.json
 
       - name: Build documents
-        run: npm run docs #set up 'docs' build script in your package.json
+        run: pnpm run docs #set up 'docs' build script in your package.json
 
       - name: tar the new docs
         run: tar -cvf newdocumentation.tar ./docs