ci: run vitest browser tests in github actions

Install chromium with playwright before pnpm test
so headless browser mode works on ubuntu-latest.

.github/workflows/ci.yml

@@ -37,5 +37,11 @@ jobs:
       - name: Run Prettier check
         run: pnpm format:check
 
+      - name: Install Playwright Chromium
+        run: pnpm exec playwright install chromium --with-deps
+
+      - name: Run tests
+        run: pnpm test
+
       - name: Build the project
         run: pnpm build