Writing a theme function and TWIG template for Instagram Block (drupal 8)

instagram-block-image.html.twig

{#
/**
 * @file
 * Default theme implementation of an Instagram image link.
 *
 * Available variables:
 * - data: The entire data array returned from the Instagram API request.
 * - href: The url to the Instagram post page.
 * - src: The source url to the instagram image.
 * - width: The display width of the image.
 * - height: The display height of the image.
 *
 * @ingroup themeable
 */
#}
{% spaceless %}
    <a class="group" target="_blank" rel="group1" href="{{ href }}">
        <img height="{{ height }}px" width="{{ width }}px" src="{{ src }}">
    </a>
{% endspaceless %}

instagram_block.module

/**
 * Implements hook_theme().
 */
function instagram_block_theme() {
  return array(
    'instagram_block_image' => array(
      'variables' => array('height' => NULL,'width' => NULL, 'src' => NULL, 'href' => NULL),
      'template' => 'instagram-block-image',
    ),
  );
}

instagram_block.render_array.inc

$content['children'][$post->id] = array(
  '#markup' => '',
  '#theme' => 'instagram_block_image',
  '#data' => $post,
  '#href' => $post->link,
  '#src' => $post->images->thumbnail->url,
  '#width' => $configuration['width'],
  '#height' => $configuration['height'],
  '#attached' => array(
    'css' => array(
      drupal_get_path('module', 'instagram_block') . '/css/block.css',
    ),
  ),
);