feat: adapter-auto support bun add

[RiskyMH]

Adds support for Bun package manager with @sveltejs/adapter-auto.

Initially, I considered adding svelte-adapter-bun to the plugin list, but since Bun works seamlessly with Node.js, it wasn't necessary!

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[changeset-bot]

🦋 Changeset detected

Latest commit: 937c7e9

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

This PR includes changesets to release 1 package

Name	Type
@sveltejs/adapter-auto	Minor

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[eltigerchino]

Thank you!