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/04-click-counter/starter.js

@@ -0,0 +1,6 @@
+let count = 0;
+
+// 任务：
+// 1. 获取数字元素和 3 个按钮
+// 2. 点击按钮时更新 count
+// 3. 每次修改后，把最新 count 渲染到页面