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/12-prepend-remove-and-link-default/README.md

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+# 练习 12：prepend、classList.remove 和链接默认行为
+
+## 目标
+
+补齐几个常见但容易漏掉的 DOM 细节操作。
+
+## 你要练什么
+
+- `prepend()`
+- `classList.remove()`
+- 链接点击事件
+- `preventDefault()`
+
+## 任务
+
+- 点击“插入到最前面”时，把一条新消息插入列表顶部
+- 点击“清除高亮”时，移除全部高亮类名
+- 点击帮助链接时，阻止默认跳转，并在页面显示提示信息
+
+## 文件
+
+- [starter.html](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/12-prepend-remove-and-link-default/starter.html)
+- [starter.js](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/12-prepend-remove-and-link-default/starter.js)
+- [answer.html](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/12-prepend-remove-and-link-default/answer.html)
+- [answer.js](/Users/lijiaqing/home/wwwroot/front-end-example/04-dom-events-async/12-prepend-remove-and-link-default/answer.js)