Add publish step

.github/workflows/ci.yml

@@ -39,3 +39,27 @@ jobs:
 
       - name: Run tests with Astro ${{ matrix.astro-version }}
         run: npm test
+  publish:
+    needs: test
+    runs-on: ubuntu-latest
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20.x'
+          registry-url: 'https://registry.npmjs.org'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Publish to npm
+        run: npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}