Add wrapper CSS classes to markup component

Patch #2 rerolled. I'm not attaching the interdiff because there are no differences between one patch and another, but it's only changing 1 line, so you can easily compare with the patch in #2.

Please, review.

People are able to add any classes they want to the markup they add to the page. It has been this way for a decade → . Is there a reason this does not work?

Hi, Liam!

Could you please provide some documentation or steps to reproduce?

The markup component just puts HTML on the page. Include any needed classes in that HTML.

The custom wrapper class can add from Webform->Setting->form and add custom class on form attributes class.
This class will add on form element.