[Feature request] JSON output

Hi, thank you for writing this tool. We have found it very useful.

However we want to integrate our generated CRD documentation into our [main documentation pages](https://docs.localstack.cloud/) which are generated by [astro](https://astro.build/). We would like to write our own markdown components to render the docs in a way that matches our style.

Are you interested in accepting a PR that renders JSON output that can be read into other documentation systems like astro? I have a [POC available here](https://github.com/elastic/crd-ref-docs/compare/master...simonrw:crd-ref-docs:json-output). If this sounds interesting to you I'm happy to continue working on it and have it accepted in this repository.

Thanks