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/03-create-and-remove/answer.js

@@ -0,0 +1,20 @@
+const addButton = document.getElementById("add-btn");
+const removeButton = document.getElementById("remove-btn");
+const taskList = document.getElementById("task-list");
+
+let taskIndex = 3;
+
+addButton.addEventListener("click", function () {
+  const item = document.createElement("li");
+  item.textContent = `新任务 ${taskIndex}`;
+  taskList.appendChild(item);
+  taskIndex += 1;
+});
+
+removeButton.addEventListener("click", function () {
+  const lastItem = taskList.lastElementChild;
+
+  if (lastItem) {
+    lastItem.remove();
+  }
+});