Update adapter entrypoint typings to be NodeNext/ESNext-compatible.

[adam-coster]

As discussed in #5110, the entry index.d.ts files of the adapters all use a node-resolution-compatible export syntax like this:

 declare function plugin(): Adapter; 
 export = plugin; 

However, all of these packages use ESM (instead of CommonJS) so they can instead use:

export default function plugin(): Adapter;

Making this change resolves a Typescript 4.7+ error where import adapter from '@sveltejs/adapter-auto'; throws a compiler error when the tsconfig.json is configured with moduleResolution set to NodeNext or ESNext.

To make this change, all of the index.js files that import these types have to have their JSDoc import statements changed to explicitly grab the default export. E.g. /** @type {import('.')} **/ ➡️ /** @type {import('.').default} **/.

Since these packages are already modules these typings are more technically correct, though it's possible that this change will result in new Typescript errors for some compiler configurations. With Typescript 4.8 (dev), I can confirm that this change results in no errors with either of the following tsconfig configurations:

// Node resolution and ES2020 targets
"compilerOptions":{
    "target": "ES2020",
    "lib": ["ES2020"],
    "module": "ES2020",
    "moduleResolution": "Node",
}

// NodeNext resolution and ESNext targtes
"compilerOptions":{
    "target": "ESNext",
    "lib": ["ESNext"],
    "module": "ESNext",
    "moduleResolution": "NodeNext",
}

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9a0b1ac

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

This PR includes changesets to release 7 packages

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

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[Rich-Harris]

thank you!