Change meta viewport tag in D8

THEMENAME.theme

<?php

/**
* Implements hook_preprocess_HOOK() for HTML document templates.
*/
function THEMENAME_preprocess_html(&$variables) {
  foreach ($variables['page']['#attached']['html_head'] as $key => $value) {
    if ($value[1] === 'viewport') {
      $value[0]['#attributes']['content'] = 'width=device-width,minimum-scale=1,initial-scale=1';
      $variables['page']['#attached']['html_head'][$key] = $value;
    }
  }
}