[fix] Allow service workers to use the $lib alias

[JeanJPNM]

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Fixes #2321 by adding the $lib alias to the build options of service workers.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5668687

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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[JeanJPNM]

Gotta wait for #2328 to be merged before this.