How can we make Hugo-specific markup presentable in /help?

A powerful feature in Hugo is the ability to create custom shortcodes. These will allow us to more easily implement content formatting options that don't exist in regular markdown (e.g, alert boxes, tabs).

However, these will only render properly on the website. Pages in /help are only processed through markdown, not Hugo, and so those would look something like this:

https://gitlab.com/gitlab-com/content-sites/handbook/-/blob/main/content/handbook/total-rewards/_index.md?ref_type=heads

(The things like {{% card header="Benefits" %}} are shortcodes that would render on a compiled website, but not /help.)

Open questions

• Q: What would we need to do in /help to make these not look so strange?
  • A: MR to rewrite output for /help: gitlab-org/gitlab!174570)
• Q: Not shortcodes, but related to /help: what do we do about page titles (moving from h1s to the title front matter attribute)
  • A: Resolved via gitlab-org/gitlab!145627 (merged)
• Q: How could we use template partials for reusable content, like the legal disclaimer introduced in !43 (merged), without obscuring that content too much in /help?
  • A: For the disclaimer, we can duplicate the content. If we need more of these, we can better solve for that then.