Adding Twig Template Suggestions for Form Elements

/**
* @param $suggestions
* @param array $variables
*/
function mytheme_theme_suggestions_input_alter(&$suggestions, array $variables) {
$element = $variables['element'];

if (isset($element['#attributes']['data-twig-suggestion'])) {
$suggestions[] = 'input__' . $element['#type'] . '__' . $element['#attributes']['data-twig-suggestion'];
}
}

/**
* @param $form
* @param \Drupal\Core\Form\FormStateInterface $form_state
* @param $form_id
*/
function mytheme_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
if ($form['#id'] == 'views-exposed-form-search-results') {
$form['actions']['submit']['#attributes']['data-twig-suggestion'] = 'search_results_submit';
$form['actions']['submit']['#attributes']['class'][] = 'search-box__button';
}
}

{#
/**
* @file
* Theme override for an 'input' #type form element.
*
* Available variables:
* - attributes: A list of HTML attributes for the input element.
* - children: Optional additional rendered elements.
*
* @see template_preprocess_input()
*/
#}