Add GitHub Actions workflow for build and deploy

.github/workflows/main.yml

@@ -0,0 +1,36 @@
+name: Build and Deploy (Main)
+
+on:
+  push:
+    branches: ['master']
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: ['20']
+
+    permissions:
+      contents: write
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: 'npm'
+
+      - name: Install packages
+        run: npm ci
+
+      - name: Run npm build
+        run: npm run build:prod
+
+      - name: Deploy to gh-pages
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          deploy_key: ${{ secrets.ACTIONS_DEPLOY_KEY }}