add-featured-to-rest.php

		add_filter('rest_prepare_post','add_featured_to_post_rest', 10, 3);
		function add_featured_to_post_rest($data, $post, $request) {
			$_data = $data->data;

			$thumbnail_id = get_post_thumbnail_id($post->ID);
			$thumbnail = wp_get_attachment_image_src( $thumbnail_id, 'thumbnail');
			$thumbnailMedium = wp_get_attachment_image_src( $thumbnail_id, 'medium');
			$thumbnailLarge = wp_get_attachment_image_src( $thumbnail_id, 'large');
			$thumbnailFull = wp_get_attachment_image_src( $thumbnail_id, 'full');

			$_data['featured_thumb_src'] = $thumbnail[0];
			$_data['featured_medium_src'] = $thumbnailMedium[0];
			$_data['featured_large_src'] = $thumbnailLarge[0];
			$_data['featured_full_src'] = $thumbnailFull[0];


			$data->data = $_data;

			return $data;
		}