Document types

[Rich-Harris]

Describe the problem

The TypeScript section of the docs documents the App namespace, but none of the types that are exported from @sveltejs/kit or the $app modules. It would be good to have this information present in a reference (albeit human-readable — none of the incomprehensible garbage you get from stuff like typedoc by default).

In addition, we could definitely make stuff like this a bit nicer to look at:

Describe the proposed solution

This could take many forms, and will probably need a bit of experimentation to get right.

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

[benmccann]

Here's an issue showing where I got using TypeDoc: #3996