Where can I set the following HTML attribute to my custom field?
Solved with formElement, at least form mobile devices. Just was I was looking for.

  /**
   * {@inheritdoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &amp;$form, FormStateInterface $form_state) {
    $element = parent::formElement($items, $delta, $element, $form, $form_state);

    $element['#accept'] = 'image/*;capture=camera';

    return $element;
  }


Thank you!