Display Featured Image Upload Instructions

Show custom image size recommendations below the Featured Image meta box to help content editors upload correctly sized images.

/*Admin Side Image Upload MSG*/

function add_featured_image_instruction($content) {
    
    global $post;
    $post_type = get_post_type();
    
    if($post_type == 'page'){
        $content .= '<p>Please upload 1240 * 666 image size </p>';
    }
    /*if($post_type == 'projects'){
        $content .= '<p>Please upload 1530 * 1438 image size </p>';
    }*/
    return $content;
}
add_filter( 'admin_post_thumbnail_html', 'add_featured_image_instruction');
/*End Message*/