Add GitHub Actions workflow to verify warning-free builds

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: Build
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build

vite.config.js

@@ -18,6 +18,11 @@ export default defineConfig({
       }
     },
     rollupOptions: {
+      onwarn(warning) {
+        if (process.env.CI) {
+          throw new Error(warning.message);
+        }
+      },
       output: {
         entryFileNames: 'app.js',
         chunkFileNames: '[name].js',