fix: adjust static attribute regex

[dummdidumm]

a + was missing
Fixes sveltejs/vite-plugin-svelte#804

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[changeset-bot]

🦋 Changeset detected

Latest commit: bb3c9c1

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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[dominikg]

/ecosystem-ci run mdsvex

[svelte-ecoystem-ci]

📝 Ran ecosystem CI: Open

suite	result
mdsvex	✅ success