Add cli command to generate docs

[CobyPear]

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Hello! I have found a need to generate the api reference docs without running a full docusaurus build. I was able to symlink this change locally and test it on a monorepo with 3 objects in the Docusaurus config, but the cli command only generated docs for the first one.

I would love to get this working to support all options in the plugins options array, as well as add tests, but I would need some help. I couldn't figure out how to access the array of options when the command was invoked.

Thanks!