Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
https://github.com/go-gitea/gitea/pull/31559/commits/61105d0618e285d97e95044bfb64415f364a4526
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

web_src/js/features/comp/QuickSubmit.ts

@@ -0,0 +1,19 @@
+export function handleGlobalEnterQuickSubmit(target) {
+  let form = target.closest('form');
+  if (form) {
+    if (!form.checkValidity()) {
+      form.reportValidity();
+    } else {
+      // here use the event to trigger the submit event (instead of calling `submit()` method directly)
+      // otherwise the `areYouSure` handler won't be executed, then there will be an annoying "confirm to leave" dialog
+      form.dispatchEvent(new SubmitEvent('submit', {bubbles: true, cancelable: true}));
+    }
+    return true;
+  }
+  form = target.closest('.ui.form');
+  if (form) {
+    form.querySelector('.ui.primary.button')?.click();
+    return true;
+  }
+  return false;
+}