adding srcset

Hi Navneil,
This is a very useful plugin.
I’ve added some extra code to add srcset capabilities in my local version & wondered if you’d thought about doing the same, or if I could contribute the small changes I’ve made to your project.
The implementation I have isn’t perfect as it requires the thumbnail size to be hard-coded in:

foreach($images as $image):
			$title = $image->post_title;
			$content = $image->post_content;
			$meta_data = wp_get_attachment_metadata($image->ID);
			$large_url = wp_get_attachment_url($image->ID, 'large');
			$large_srcset = wp_get_attachment_image_srcset( $image->ID,'large', $meta_data);
			$thumbnail_url = wp_get_attachment_thumb_url($image->ID);
			$thumb_srcset = wp_get_attachment_image_srcset( $image->ID,array(150,150), $meta_data);
			$url = get_post_meta($image->ID, $field . '_url', true);
			$target = get_post_meta($image->ID, $field . '_target', true);
			$array[] = array(
				'id' => $image->ID,
				'title' => $title,
				'caption' => $content,
				'large_image_url' => $large_url,
				'large_srcset' => $large_srcset,
				'thumbnail_image_url' => $thumbnail_url,
				'thumb_srcset' => $thumb_srcset,
				'url' => $url,
				'target' => $target
			);
		endforeach;

Best wishes,
Guy