[fix] allow Vite plugins to output mutable assets

[benmccann]

@userquin is trying to get vite-plugin-pwa working with SvelteKit. That plugin adds a mutable manifest to the bundle. Since the bundle is written to the outDir we need the outDir to be set to client instead of client/immutable

[changeset-bot]

🦋 Changeset detected

Latest commit: 26caa80

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

This PR includes changesets to release 1 package

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@sveltejs/kit	Patch

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[benmccann]

Looks like adapter-static is ending up with immutable in the path twice somehow:

cd packages/adapter-static/test/apps/spa
pnpm start
404 - /_app/immutable/immutable/start-d357e0b9.js

[benmccann]

this looks good to me. thanks for the help getting it working, Rich!