Update controller update to allow clean MD render

What does this MR do and why?

In order to render the help markdown document inside the UI dropdown I need a backend markdown renderer to be able to output just the markdown body as HTML. The current version is rendering any help markdown as (https://about.gitlab.com/handbook/markdown-guide/) SSG with header and footer.

Issue: #329234 (closed)

1/4

• Update controller update to allow clean MD render (merged) 👈 this MR
  • Markdown Drawer - shared Vue component (merged)
    • Add more data to the search context
      • Add syntax options drawer to topBar component

Screenshots or screen recordings

How to set up and

1. Checkout this branch
2. Request any docs document to receive pure MD body render (eg. curl "http://localhost:3000/help/drawers/user/search/global_search/advanced_search_syntax.html")

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #329234 (closed)