Add storybook demo for CheckboxControl (#3030)

* story for CheckboxControl aka Checkbox

* Rename exported story to Default and use correct component name

This keeps our stories more consistent

assets/js/base/components/checkbox-control/stories/index.js

@@ -0,0 +1,27 @@
+/**
+ * External dependencies
+ */
+import { text } from '@storybook/addon-knobs';
+import { useState } from 'react';
+
+/**
+ * Internal dependencies
+ */
+import CheckboxControl from '../';
+
+export default {
+	title: 'WooCommerce Blocks/@base-components/CheckboxControl',
+	component: CheckboxControl,
+};
+
+export const Default = () => {
+	const [ checked, setChecked ] = useState( false );
+
+	return (
+		<CheckboxControl
+			label={ text( 'Label', 'Yes please' ) }
+			checked={ checked }
+			onChange={ ( value ) => setChecked( value ) }
+		/>
+	);
+};