Full width Gutenberg

gutenberg-full-width.php

<?php 

function radish_gutenberg_full_width() {
	echo '<style>
		body.gutenberg-editor-page .editor-post-title__block, body.gutenberg-editor-page .editor-default-block-appender, body.gutenberg-editor-page .editor-block-list__block {
			max-width: none !important;
		}
		.block-editor__container .wp-block {
			max-width: none !important;
	}
	</style>';
}

add_action( 'admin_head', 'radish_gutenberg_full_width' );