add CI build workflow

.github/workflows/build.yaml

@@ -0,0 +1,24 @@
+name: Check build
+
+on: [push, pull_request]
+
+jobs:
+  build-check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Run build check
+        run: |
+          npm run build
+          npm run build:pwa