Add json schema-powered shiki twoslash tooltips to docsite

[cspotcode]

Building off #1670

Add json schema-powered shiki twoslash tooltips to docsite

Will require a totally new kind of shiki twoslash tooltip provider, implemented as a separate open-source project.

But the benefit is, our docs have lots of tsconfig.json examples. Would be nice to have fancy tooltips for all of them.