[REQ] Docusaurus Markdown support

Is your feature request related to a problem? Please describe.

Docusaurus is a well-known static site generator. (It is used by https://openapi-generator.tech as well.)

We tried to place the markdown files generated by markdown generator directly under Docusaurus, and find that there is extra work before the markdown files well parsed by Docusaurus.

Describe the solution you'd like

According to https://docusaurus.io/docs/create-doc, following header is required for each markdown file:

---
id: greeting
title: Hello
---

It'd be nice to add a logic to include this header in the markdown generator.

Another change that's needed is described as a bug in https://github.com/OpenAPITools/openapi-generator/issues/9407

Describe alternatives you've considered

Not really, other than manually update each markdown file.

Additional context

This rendered page below is based on a hand curated markdown file generated by markdown generator. We can see it's still imperfect.

Start at the markdown generator and review issue #9407 for the related parsing problem. The change is done when generated Markdown files include Docusaurus-compatible front matter with the required id and title fields; the payload names no specific source file or test.