Fix loading button with invalid form (go-gitea#20754)

Previously, if a invalid form was submitted (for example issue with no
title), the form could not be re-submitted again because the button
would not stay stuck in loading state. Fix that by hooking the 'submit'
event instead which triggers only when the form is valid.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/js/features/common-global.js

@@ -142,16 +142,12 @@ export function initGlobalCommon() {
     }
   });
 
-  // loading-button this logic used to prevent push one form more than one time
-  $(document).on('click', '.button.loading-button', function (e) {
-    const $btn = $(this);
-
-    if ($btn.hasClass('loading')) {
-      e.preventDefault();
-      return false;
-    }
-
-    $btn.addClass('loading disabled');
+  // prevent multiple form submissions on forms containing .loading-button
+  document.addEventListener('submit', (e) => {
+    const btn = e.target.querySelector('.loading-button');
+    if (!btn) return;
+    if (btn.classList.contains('loading')) return e.preventDefault();
+    btn.classList.add('loading');
   });
 }