title: how to add awordpress plugin custom thumbnial
body: <p>i am create a wordpress plugin, this plugin add custompost but this post not see featured image </p>
  
  <pre><code>    add_theme_support('post-thumbnails',array('km-lightbox','post'));
      add_action( 'init', 'create_posttype_light_box' );
      function create_posttype_light_box() {
    register_post_type( 'km-lightbox',
      array(
        'labels' =&gt; array(
          'name' =&gt; __( 'Lightboxs' ),
          'singular_name' =&gt; __( 'lightbox' )
        ),
        'public' =&gt; true,
        'supports'=&gt; array('title', 'editor','thumbnail'  ),
        'has_archive' =&gt; true,
        'rewrite' =&gt; array('slug' =&gt; 'lightbox')
        )
    );
  }
  </code></pre>