feat: add GitHub Actions workflow for staging deployment

Author: zzhenryquezz

.github/workflows/staging.yml

@@ -0,0 +1,37 @@
+name: Deploy staging instance
+
+on:
+  push:
+    branches:
+      - develop
+
+permissions:
+  contents: write # allow GITHUB_TOKEN to push to gh-pages
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Setup Node.js with cache
+        uses: actions/setup-node@v3
+        with:
+          node-version: '23'
+          cache: 'npm' # enables automatic caching based on package-lock.json
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Generate static site
+        run: npm run build
+
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }} # built-in token, no manual secret needed
+          publish_dir: ./dist
+          publish_branch: build-staging
+