New Language Support: Markdown

[CoinsNaulty]

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

Is it possible to create a "Markdown" formatted generator using Open-RPC/generator? If so, it would be great to document that functionality. If not, it would be great to support such functionality!

Describe the solution you'd like

Generate a single Markdown page when language type is set to markdown

Describe alternatives you've considered

OpenAPI generator has this type of functionality, and I think it would be great to have the same functionality for JSON-RPC based specs.