Showcase Figure/Figcaption together and with image

Problem/Motivation

As it is now, Styleguide by default shows the HTML tags <figure> and <figcaption> in isolation (as if they were inline tags, like <strong>) and with text:

    $items['figcaption'] = array(
      'title' => $this->t('Figcaption'),
      'content' => [
        '#type' => 'inline_template',
        '#template' => '{{ pre }} <figcaption>{{ figcaption }}</figcaption> {{ post }}.',
        '#context' => [
          'pre' => $this->generator->words(3, 'ucfirst'),
          'figcaption' => $this->generator->words(3),
          'post' => $this->generator->words(4),
        ],
      ],
    );
    $items['figure'] = array(
      'title' => $this->t('Figure'),
      'content' => [
        '#type' => 'inline_template',
        '#template' => '{{ pre }} <figure>{{ figure }}</figure> {{ post }}.',
        '#context' => [
          'pre' => $this->generator->words(3, 'ucfirst'),
          'figure' => $this->generator->words(3),
          'post' => $this->generator->words(4),
        ],
      ],
    );

I think this is not the best outcome, since those tags are required to be used together and <figure> is used to hold an image-like element, not text.

For reference, MDN states that

"The HTML or Figure Caption element represents a caption or legend describing the rest of the contents of its parent element." (https://developer.mozilla.org/en-US/docs/Web/HTML/Element/figcaption)

And;

Usually a is an image, illustration, diagram, code snippet, etc., that is referenced in the main flow of a document, but that can be moved to another part of the document or to an appendix without affecting the main flow.(link)

As a result, the Styleguide is failing to provide with an accurate representation of the HTML element as it will be used in real code.

Proposed resolution

Merge both figure and figcaption under a single element, since they can't be found in isolation and <figcaption> is always the child of a <figure>.

Change the content of <figure> to include an image instead of text.