Get field configuration

field_config.php

public static function getFieldConfig($nodeBundle, $field_name) {
  $entity_field_manager = \Drupal::service('entity_field.manager');
  $entity_field_manager->useCaches(FALSE);
  $fieldsSettings = $entity_field_manager->getFieldDefinitions('node', $nodeBundle);
  if (!isset($fieldsSettings[$field_name])) {
    return NULL;
  }
  /** @var \Drupal\field\Entity\FieldConfig $fieldSetting */
  $fieldSetting = $fieldsSettings[$field_name];
  return $fieldSetting;
}