feat: add TypeScript lessons and learning panel

- Introduced a new script to check TypeScript lesson files for errors.
- Created a main TypeScript file to render lessons and their details.
- Added lesson definitions with starter and answer codes.
- Implemented a user interface for navigating and running lessons.
- Styled the application with CSS for a better user experience.
- Updated README to reflect the new TypeScript section and usage instructions.

05-es6-plus/08-fetch-and-json/starter.js

@@ -0,0 +1,11 @@
+const loadButton = document.getElementById("load-btn");
+const status = document.getElementById("status");
+const output = document.getElementById("output");
+
+// 任务：
+// 1. 点击按钮后把状态改成“加载中...”
+// 2. 用 fetch 请求 https://jsonplaceholder.typicode.com/posts/1
+// 3. 用 await 等待响应对象
+// 4. 调用 res.json() 解析数据
+// 5. 把 title 和 body 渲染到页面
+// 6. 失败时显示“加载失败”