Showing a wysiwyg textarea input type
A WYSIWYG (pronounced "wiz-ee-wig") editor or program is one that allows a developer to see what the end result will look like while the interface or document is being created. WYSIWYG is an acronym for "what you see is what you get". ( whatis.techtarget.com )
$this->form[] = ['label'=>'Content','name'=>'content','type'=>'wysiwyg'];