Add GitHub Action for publishing

.github/workflows/publish.yml

@@ -0,0 +1,29 @@
+name: Publish speedlify
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20.x
+
+      - name: Build pages
+        run: |
+          npm ci
+          npm run build
+
+      - name: Publish to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          publish_dir: ./_site
+          github_token: ${{ secrets.GITHUB_TOKEN }}