[feat] allow URL in goto

[GauBen]

A simple type change to allow writing

const url = new URL(then, $page.url);
await goto(url);

instead of

const url = new URL(then, $page.url);
await goto(url.toString());

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🦋 Changeset detected

Latest commit: dba8c67

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

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Patch

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[Rich-Harris]

thank you!