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/answer.js

@@ -0,0 +1,30 @@
+function fakeFetchCourses() {
+  return new Promise(function (resolve) {
+    setTimeout(function () {
+      resolve(["DOM 获取元素", "事件监听", "异步基础"]);
+    }, 800);
+  });
+}
+
+const loadButton = document.getElementById("load-btn");
+const statusText = document.getElementById("status-text");
+const courseList = document.getElementById("course-list");
+
+loadButton.addEventListener("click", function () {
+  statusText.textContent = "加载中...";
+  courseList.innerHTML = "";
+
+  fakeFetchCourses()
+    .then(function (courses) {
+      courses.forEach(function (course) {
+        const item = document.createElement("li");
+        item.textContent = course;
+        courseList.appendChild(item);
+      });
+
+      statusText.textContent = "加载完成";
+    })
+    .catch(function () {
+      statusText.textContent = "加载失败";
+    });
+});