ci: Add a build step so we are more prepared for playwright

.github/workflows/firebase-hosting-pull-request.yml

@@ -34,6 +34,8 @@ jobs:
           node-version-file: package.json
       - name: Install Dependencies
         run: npm install
+      - name: Build
+        run: npm run build
       - name: Install Playwright Browsers
         run: npx playwright install --with-deps
       - name: Run integration tests