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/05-form-submit-and-prevent-default/answer.js

@@ -0,0 +1,18 @@
+const form = document.getElementById("todo-form");
+const input = document.getElementById("todo-input");
+const list = document.getElementById("todo-list");
+
+form.addEventListener("submit", function (event) {
+  event.preventDefault();
+
+  const value = input.value.trim();
+
+  if (!value) {
+    return;
+  }
+
+  const item = document.createElement("li");
+  item.textContent = value;
+  list.appendChild(item);
+  input.value = "";
+});