Custom configuration textarea with editor

Hi all,

New on the Drupal Forums, I have come across something I wouldn't say is a problem but more of something that's bugging me. I'm building a custom module for newsletter signups, functionality is great and it all works well. This module has a configuration page in which there's a confirmation message textarea.

Is there anyway to configure the textarea to be an editor? I'm thinking in future if any users of the backend want to edit it and aren't familiar with HTML.

I have looked in the Form API but not seen anything that makes me think it's part of core. Anyone got any helpful advice?