fix: js.exports.createNamed fails if the AST contains a function declaration

[jycouet]

Closes #1083

Description

js.exports.createNamed crashed with TypeError: Cannot read properties of undefined (reading '0') when the AST contained an exported function (or class) declaration. The lookup blindly cast the export's declaration to VariableDeclaration. Now it branches on declaration type and reads id.name for function/class declarations.

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[changeset-bot]

🦋 Changeset detected

Latest commit: ebe1350

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

This PR includes changesets to release 2 packages

Name	Type
@sveltejs/sv-utils	Patch
sv	Patch

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commit: ebe1350

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