Add presubmit to build site for each pr.

.github/workflows/build.yml

@@ -0,0 +1,23 @@
+---
+name: Build static site
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup node
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: "npm"
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Build with next.js
+        run: npm run build