Add ACF fields to WordPress Page Meta field

acf.php

<?php

/**
 * Add ACF to Post meta stuff.
 */
function my_rest_prepare_post( $data, $post, $request ) {
	$data->data['meta'] = array_merge($data->data['meta'], get_fields($post->ID));
	return $data;
}
add_filter( 'rest_prepare_page', 'my_rest_prepare_post', 10, 3 );