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/12-prepend-remove-and-link-default/answer.js

@@ -0,0 +1,31 @@
+const prependButton = document.getElementById("prepend-btn");
+const clearActiveButton = document.getElementById("clear-active-btn");
+const helpLink = document.getElementById("help-link");
+const hintText = document.getElementById("hint-text");
+const messageList = document.getElementById("message-list");
+
+let messageIndex = 1;
+
+prependButton.addEventListener("click", function () {
+  const item = document.createElement("li");
+  item.className = "item active";
+  item.textContent = `新插入的提醒 ${messageIndex}`;
+  messageList.prepend(item);
+  hintText.textContent = "已把一条消息插入到最前面";
+  messageIndex += 1;
+});
+
+clearActiveButton.addEventListener("click", function () {
+  const items = document.querySelectorAll(".item");
+
+  items.forEach(function (item) {
+    item.classList.remove("active");
+  });
+
+  hintText.textContent = "已移除全部高亮状态";
+});
+
+helpLink.addEventListener("click", function (event) {
+  event.preventDefault();
+  hintText.textContent = "已阻止默认跳转";
+});