Drupal Form API doesn't offer a native HTML type="reset" button known from the W3C:
https://www.w3.org/TR/2012/WD-html-markup-20121025/input.reset.html
So if you ever need one, this might be a good starting point in Drupal 8+:
'reset' => [
'#type' => 'html_tag',
'#tag' => 'input',
'#attributes' => [
'class' => 'button button--reset',
'type' => 'reset',
'value' => $this->t('Reset'),
],
],