function crasdt_form_system_theme_settings_alter(&$form, DrupalCoreFormFormStateInterface &$form_state) {

  $form['shepherd_img'] = array(
    '#type'          => 'managed_file',
    '#title'         => t('Imagem do Pastor'),
    '#default_value' => theme_get_setting('shepherd_img'),
    '#description'   => t("Imagem do Pastor que aparece no cabeçalho."),
    '#upload_location' => 'public://appearance/',
    '#upload_validators'  => array(
      'file_validate_extensions' => array('gif png jpg jpeg'),
      'file_validate_image_resolution' => array('400x400', '200x200'),
    ),
    '#weight' => 0
  );

  // Work-around for this bug: https://drupal.org/node/1862892
  $theme_settings_path = drupal_get_path('theme', 'crasdt') . '/theme-settings.php';
  if (!in_array($theme_settings_path, $form_state->getBuildInfo()['files'])) {
    $newBuildInfo = $form_state->getBuildInfo();
    $newBuildInfo['files'][] = $theme_settings_path;
    $form_state->setBuildInfo($newBuildInfo);
  }
  $form['#submit'][] = 'crasdt_form_system_theme_settings_submit';
}

function crasdt_form_system_theme_settings_submit(&$form, DrupalCoreFormFormStateInterface &$form_state) {
    $file = DrupalfileEntityFile::load($form_state->getValue('shepherd_img')[0]);
    $file->setPermanent();
    $file->save();
}