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/08-promise-and-render/starter.js

@@ -0,0 +1,14 @@
+function fakeFetchCourses() {
+  return new Promise(function (resolve) {
+    setTimeout(function () {
+      resolve(["DOM 获取元素", "事件监听", "异步基础"]);
+    }, 800);
+  });
+}
+
+// 任务：
+// 1. 获取按钮、状态文字、列表
+// 2. 点击按钮后显示“加载中”
+// 3. 调用 fakeFetchCourses()
+// 4. 用 then 渲染课程列表
+// 5. 用 catch 处理错误