JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdn.ckeditor.com/4.4.3/standard/ckeditor.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/ckeditor/4.4.1/adapters/jquery.min.js"></script>
<label for="data">Describe the Issue</label>
<textarea name="data" id="data" placeholder="Describe the issue in full. Paste any screenshots in to this field, or attach them if saved to a file." cols="30" rows="6">Lorem ipsum default text to determine .cke body {margin:...} (hopefully 0 px) at a glance</textarea>

CSS

.cke body { margin:0; }

JavaScript

CKEDITOR.stylesSet.add( 'style_updates', [
    // ATTEMPT 1
	// Block-level styles...this is for the dropdown menu (not shown in current config)
	{ name: 'Body Margin Fix', element: 'body', styles: { margin: '10px' } }
]);

editor = $('textarea').ckeditor( function(editor){
    // ATTEMPT 2
	//callback `this` refers to CKEDITOR.editor
	this.ckeditorGet().addCss('body { margin:10px; }')
}, {
    // ATTEMTP 3
	addCss: 'body { margin:10px; }',
	stylesSet: 'styles_updates',
	uiColor: '#FFFFFF',
	scayt_autoStartup: true,
	autoGrow_onStartup: true,
	enterMode: CKEDITOR.ENTER_BR,
	removePlugins: 'elementspath, resize',
	toolbar: [
		{ name: 'basicstyles', groups: [ 'basicstyles', 'cleanup' ], items: [ 'Bold', 'Italic', 'Underline' ] },
		{ name: 'clipboard', groups: [ 'clipboard', 'undo' ], items: [ 'PasteFromWord', 'Undo', 'Redo' ] },
		{ name: 'links', items: [ 'Link', 'Unlink' ] },
		{ name: 'editing', groups: [ 'spellchecker' ], items: [ 'Scayt' ] },
		{ name: 'tools', items: [ 'Maximize' ] }
	]
// ATTEMPT 4
}).ckeditorGet().addCss('body { margin:10px; }');