replace %svelte.assets% with relative path

[Rich-Harris]

Fixes #2697, supersedes #3088. Replaces %svelte.assets% in src/app.html with a relative path to the root (or to paths.assets in production, if specified).

In other words this...

<link rel="icon" type="image/png" href="%svelte.assets%/favicon.png" />

...will work regardless of whether paths.assets is set, and will also work if you've set paths.base (or, in future, if we implement dynamic basepaths somehow) because a page like /custom-basepath/foo/bar/baz will link to ../../favicon.png, which resolves to /custom-basepath/favicon.png. It will still work if trailingSlash is "always" .

(Note that there's currently a bug around paths.base — static assets aren't served from there in dev mode. Needs fixing separately.)

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[changeset-bot]

🦋 Changeset detected

Latest commit: a854e31

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

This PR includes changesets to release 2 packages

Name	Type
@sveltejs/kit	Patch
create-svelte	Patch

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[Conduitry]

Also adjacent: #3231 and #3232

[Rich-Harris]

The deployments are failing because they're trying to build with the most recent released version of Kit, which doesn't know how to handle %svelte.assets% and is therefore resulting in a malformed URI error when prerendering. We can safely ignore

[Conduitry]

Should this PR be marked as resolving #3231 now? There should be a changeset added for the create-svelte change in any case.

I didn't look closely at what was happening in #3232.

[Rich-Harris]

It should, yeah. I need to look into #3232

[dreitzner]

@Rich-Harris should I port the relevant docs over from #3088 ?