Publish the API documentation

[javagl]

The API documentation of the validator should be hosted at a public place.

Right now, the documentation can be built via npm run docs. The result is stored as a bunch of interlinked Markdown files in the build/docs folder. But they should eventually be hosted at a public place. Where and how this will be done has to be decided.

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^{Note: The current release version of the validator is a 0.x.y version, tagged as "beta", for early previews and feedback. The API surface is intentionally kept minimal for now, as more precise requirements for the use case as a libarary are gathered.}