improve TypeScript typings for DefaultMarker

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: b722cd8c48751a1999b563a1d81030e374427a86

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

This PR includes changesets to release 1 package

| Name | Type | | --------------- | ----- | | svelte-maplibre | Patch |

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[dimfeld]

Thanks again!