Description in TableFormatter

Add description en tableformater
Add new code in line 27 and 31
change file: TableFormatter.php

<?php

namespace Drupal\file\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FieldItemListInterface;

/**
 * Plugin implementation of the 'file_table' formatter.
 *
 * @FieldFormatter(
 *   id = "file_table",
 *   label = @Translation("Table of files"),
 *   field_types = {
 *     "file"
 *   }
 * )
 */
class TableFormatter extends FileFormatterBase {

  /**
   * {@inheritdoc}
   */
  public function viewElements(FieldItemListInterface $items, $langcode) {
    $elements = array();

    if ($files = $this->getEntitiesToView($items, $langcode)) {
      $header = array(t('Attachment'), t('Size'));
      $rows = array();
      foreach ($files as $delta => $file) {
        $item = $file->_referringItem; #new Code
        $rows[] = array(
          array(
            'data' => array(
              '#theme' => 'file_link',
              '#file' => $file,
              '#description'=> $item->description, #new Code
              '#cache' => array(
                'tags' => $file->getCacheTags(),
              ),
            ),
          ),
          array('data' => format_size($file->getSize())),
        );
      }

      $elements[0] = array();
      if (!empty($rows)) {
        $elements[0] = array(
          '#theme' => 'table__file_formatter_table',
          '#header' => $header,
          '#rows' => $rows,
        );
      }
    }

    return $elements;
  }

}

?>