Add property plugin example usage

Hi @alison. I ended up hitting a similar issue on a new site. It looks like I had solved it previously using a preprocess hook, like this:

function mymodule_preprocess_paragraph(&$variables): void {
  /** @var \Drupal\paragraphs\Entity\Paragraph $paragraph */
  $paragraph = $variables['paragraph'];
  $behaviorSettings = $paragraph->getAllBehaviorSettings();

  // Set style option behaviors as a logical template variable.
  if (!empty($behaviorSettings['style_options'])) {
    foreach ($behaviorSettings['style_options'] as $key => $style) {
      if (isset($style['property'])) {
        $variables['style_options'][$key] = $style['property'];
      }
    }
  }
}

and then in Twig was able to get at it with {{ style_options.my_style_option }}.

Thanks so much for sharing @sethhill! We've paused on our internal project to experiment with Mercury Editor, but I've got this saved for if/when we finally circle back to that effort (🤞🤞). And meanwhile, I'll share this with the other person I know who's been experimenting with Mercury Editor.