fix(test): fix window.SubmitEvent polyfill by using a class instead of a function (it requires a prototype)

Author: Kocal

src/Turbo/assets/test/setup.js

@@ -8,4 +8,4 @@
  */
 
 // polyfill for some odd error inside of Turbo in the test environment
-window.SubmitEvent = () => {};
+window.SubmitEvent = class {};