Rewrite urls in CSS for CDN/Bucket

Add the following to functions.php

add_filter( 'fl_builder_render_css', function( $css, $nodes, $global_settings, $include_global ) {
	$site_url = 'https://example.com';
	$cdn_url  = 'https://123456abcdef.cloudfront.net';

	$css = str_replace( $site_url, $cdn_url, $css );
	return $css;
}, 10, 4 );