fix: add labels to @const tags and props

[Rich-Harris]

Adds missing labels to @const and props

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[changeset-bot]

🦋 Changeset detected

Latest commit: 1081ab1

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

This PR includes changesets to release 1 package

Name	Type
svelte	Patch

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Playground

pnpm add https://pkg.pr.new/svelte@16454

[Rich-Harris]

as with #16452, gonna self-merge this because i need it