Naming templates based on page title in drupal 8.

mytheme.theme

function my_theme_theme_suggestions_page_alter(array &$suggestions, array $variables) {
  // Naming templates based on page title.
  if ($node = \Drupal::routeMatch()->getParameter('node')) {
    $translation = $node->getTranslation('en');
    $suggestions[] = 'page__node__' . strtolower($translation->title->value);
    $title = $node->getTitle();
    foreach ($suggestions as &$replace) {
      $replace = str_replace(' ', '_', $replace);
    }
  }
}