Adding Markdown file to x-introItems

[0xsj]

New to spectaql, and really enjoying the experience so far.

Is there a way to add markdown files in the description of the x-introItems?
I have some copy for the documentation that I would like to keep in a separate file, and read from it instead of having the raw text inside of the description.

`
x-introItems:

• title: some title
• (import MD with copy file here)
  `

[ledburyb]

I'm also wanting to use something like this, I had a go at a PR but I'm not familiar enough with the codebase to work it all out.

[newhouse]

Will be supported in 1.0.0, which is not out yet.

Fixed via #227