feat(webui): add footer

Also make it automatically open the web when you launch the app.

web/assets/index.js

@@ -80,6 +80,8 @@ getLessonButton.addEventListener('click', async () => {
         for (const [id, video] of Object.entries(ids)) {
             promises.push(async () => {
                 const checkbox = document.querySelector(`#${id}`);
+                // Disable the checkbox since the user can't download the same video twice
+                checkbox.disabled = true;
                 if (!checkbox.checked) {
                     return;
                 }