Add settings to enable visual or text editor for TinyMCE

[JoryHogeveen]

Description

This will allow users to optionally disable the visual editor or the quicktags.

Related GitHub issue(s)

Fixes #6176

Changelog text for these changes

PR checklist

• [ ] I have tested my own code to confirm it works as I intended.
• [ ] My code follows the WordPress Coding Standards.
• [ ] My code follows the WordPress Inline Documentation Standards.
• [ ] My code includes automated tests for PHP and/or JS (if applicable).