Page layout

layout.css

.layout-container {
  max-width: 64rem;
}

page.html.twig

<div class="layout-container">
  <header role="banner">
    {{ page.header }}
  </header>
  <main role="main">
    <a id="main-content" tabindex="-1"></a>{# link is in html.html.twig #}
    <div class="layout-content">
      {{ page.content }}
    </div>{# /.layout-content #}
  </main>
  {% if page.footer %}
    <footer role="contentinfo">
      {{ page.footer }}
    </footer>
  {% endif %}
</div>{# /.layout-container #}