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.

05-es6-plus/03-arrow-functions/starter.js

@@ -0,0 +1,14 @@
+function getLevel(score) {
+  return score >= 80 ? "达标" : "继续练习";
+}
+
+function add(a, b) {
+  return a + b;
+}
+
+const tracks = ["DOM", "异步", "模块化"];
+
+// 任务：
+// 1. 把 getLevel 改成箭头函数
+// 2. 把 add 改成箭头函数
+// 3. 用 map + 箭头函数生成 ["[DOM]", ...]