add types to pkg.exports

[Rich-Harris]

fixes #5028 (I think?). No types for @sveltejs/kit/* but I don't think we need them because of types/ambient.d.ts

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

Changesets

• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. All changesets should be patch until SvelteKit 1.0

[changeset-bot]

🦋 Changeset detected

Latest commit: 5267a10

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
@sveltejs/adapter-auto	Patch
@sveltejs/adapter-cloudflare	Patch
@sveltejs/adapter-cloudflare-workers	Patch
@sveltejs/adapter-netlify	Patch
@sveltejs/adapter-node	Patch
@sveltejs/adapter-static	Patch
@sveltejs/adapter-vercel	Patch
@sveltejs/amp	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[mrkishi]

I won't pretend to know why it's needed, but it seems to work here both in VSCode and tsc.