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.

04-dom-events-async/02-text-class-style/README.md

@@ -0,0 +1,25 @@
+# 练习 2：修改文本、类名和样式
+
+## 目标
+
+学会改元素内容、切换类名和设置简单样式。
+
+## 你要练什么
+
+- `textContent`
+- `classList.add`
+- `classList.remove`
+- `style`
+
+## 任务
+
+- 把标题改成“今天已完成 DOM 练习”
+- 给状态标签加上完成样式
+- 修改说明文字颜色
+
+## 文件
+
+- [starter.html](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/02-text-class-style/starter.html)
+- [starter.js](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/02-text-class-style/starter.js)
+- [answer.html](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/02-text-class-style/answer.html)
+- [answer.js](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/02-text-class-style/answer.js)