Return proper AjaxResponse on ajaxSubmit

Rerolled for

Fixed for branch: https://git.drupalcode.org/issue/votingapi_widgets-3333559/-/tree/333355...

I created a MR from the patch so that we can do automated testing on it.

I think returning a form array is the preferred method in this case.
Regardless, if you return an AjaxResponse, it can't be an empty response - you have to ->addCommand() and provide the form array to the response.

Bottom line, not a bug, since we are currently using the recommended method for this simple use-case, and needs work because returning an empty AjaxResponse will not work.

Working on it.

Made changes suggested in #14,
Please review.

Needs tests.

"use" statements need to be alphabetical.

What about #wrapper ?