fix: Add Node.js setup for Netlify CLI

- preview-netlify action requires npm to install netlify-cli
- RunsOn custom AMI doesn't have Node.js pre-installed
- Add actions/setup-node@v4 before preview deploy step

Author: mmcky

.github/workflows/ci.yml

@@ -86,6 +86,10 @@ jobs:
         with:
           name: execution-reports-html
           path: _build/html/reports
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
       - name: Preview Deploy to Netlify
         uses: quantecon/actions/preview-netlify@v0.6.0
         with: