Auto-generate Client API Docs

[timoxley]

Current auto-generated docs only include DataUnion docs.
This PR includes auto-generated docs for the rest of top-level client APIs.
Also added some minor annotation changes to expose some things which shouldn't be @internal e.g. client.resend, and started giving descriptions to config properties.
Some classes and methods have the @category Important annotation in order to highlight them in the docs.

This PR also includes updated DU docs, due to changes in #220

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New pages look something like this:

Entry

StreamrClient

Config

[fonty1]

Excellent! LGTM, I suppose the GitHub Pages will update every time the /docs folder is updated on the master branch?

[timoxley]

I suppose the GitHub Pages will update every time the /docs folder is updated on the master branch?

Correct 👍

[jtakalai]

LGTM, though maybe should docs be generated and published as a Github Action, instead of pushed to source control?

[timoxley]

though maybe should docs be generated and published as a Github Action, instead of pushed to source control?

Good point, that would be better.

[timoxley]

Going to add the docs in a new workflow. Merging so Actions picks up the new workflow.

[timoxley]

Hm, Actions UI wasn't showing the new workflow, but now it is. ok. Cool. Will open new PR to iterate on that.