Full HTML demo pattern

The HTML for the demo page can differ from the code samples displayed in the code pattern tabs. To achieve this, include the full HTML for the page in the demo.md file in the patterns directory, and ommit the layout property in the frontmatter. You still neeed to include the patternId in the frontmatter.

---
patternId: full-html-demo
---

<!DOCTYPE html>
<html>
  <head></head>
  <body>I'm a full HTML demo.</body>
</html>