[breaking] add embedded option, turned off by default

[dummdidumm]

Migration

If you relied on the new behavior introduced in #7766, you can get that back by adding embedded: true to your svelte.config.js:

export default {
  kit: {
+    embedded: true
  }
}

PR description

Closes #7940
Closes #4935
Adds a new option which defaults to false. If true, events related to navigation etc are listened to on the target element rather the html root

Open questions solved:

• approach sensible? I figured using the define feature for this is the most straightforward and treeshakes nicely it is
• using data-sveltekit-root instead (as discussed in the issue)? Advantage: no config option, more control ("I use popper.js with embedded Kit, and it adds itself to some tag higher than the target). Disadvantage: feels clunky, a little more startup code that might not be as reliable. option is the way to go

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Tests

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Changesets

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9e7c889

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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Name	Status	Preview	Updated
kit	✅ Ready (Inspect)	Visit Preview	Dec 7, 2022 at 10:52AM (UTC)
kit-svelte-dev	✅ Ready (Inspect)	Visit Preview	Dec 7, 2022 at 10:52AM (UTC)

[arackaf]

🎉🥳🎊🍾

[benmccann]

we need a docs change still for this one

[Rich-Harris]

I'm not sure how best to add docs for this beyond https://kit-svelte-e9gz8bfaa-svelte.vercel.app/docs/configuration#embedded? (Though I guess it should probably mention the params stuff. Oh, and we can skip sending params from the server unless embedded: true. Will update in a sec)

This is a niche enough thing that it probably doesn't warrant a new section of the docs — I think it's probably enough that people can find it via the config docs, and we can point people to it as and when needs arise.

[Conduitry]

I'm in favor of not documenting this further than this note in the configuration docs, especially since the old default behavior was (it would seem) solely for the benefit of the NY Times and I'm sure they have other out-of-band ways of complaining to you.

[arackaf]

Should we investigate which irresponsible individual at the NYT was shipping things to production using a pre-beta application framework?

[johnnysprinkles]

Awesome, I just got SvelteKit 1.0.0-next.584 and can confirm #4935 is resolved. By the way, this is for a SvelteKit app related to the recently announced Apple Music Sing feature.

[patriciatiffany]

I came here from the docs, trying to figure out what embedded: true does, exactly. I have an inkling it will be useful for my use cases (I use exclusively adapter-static), but that short phrase in the docs isn't quite enough for me to understand. Could I get some context?