add official Chrome feature demos

public/demo/view-transitions/index.html

@@ -0,0 +1,29 @@
+<!doctype html>
+<html lang="zh-CN">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>View Transitions Demo</title>
+    <link rel="stylesheet" href="./styles.css" />
+  </head>
+  <body>
+    <main class="shell">
+      <section class="hero">
+        <p class="eyebrow">Chrome UI capability</p>
+        <h1>View Transitions</h1>
+        <p>点击不同状态，观察浏览器把 DOM 更新包装成一次连续过渡。没有支持时，页面仍然即时切换。</p>
+      </section>
+
+      <section class="app" id="app">
+        <nav class="tabs" aria-label="Demo states">
+          <button class="active" data-view="orders">订单</button>
+          <button data-view="analytics">分析</button>
+          <button data-view="settings">设置</button>
+        </nav>
+        <div class="panel" id="panel"></div>
+      </section>
+    </main>
+
+    <script src="./app.js" type="module"></script>
+  </body>
+</html>