fix: lazily load CSS for CSR dynamically imported components

[teemingc]

fixes #13546

This PR changes server nodes from always loading dynamically imported component's styles and fonts to only loading them if they are used during SSR (to avoid FOUC). This fixes lazy loading of components on the client, only retrieving the styles when needed.

We can tell which deps are used during SSR by analysing the deps of the node with both the server manifest and the client manifest, then comparing the results. If a style or font is missing from the server deps, it's probably only used on the client. Therefore, it should be safe to load lazily.

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🦋 Changeset detected

Latest commit: f1e419d

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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[onesinghashish]

@eltigerchino thanks for the fix. eagerly waiting for the release :)

[teemingc]

@eltigerchino thanks for the fix. eagerly waiting for the release :)

You can try it out right now while waiting for the official release. Just run:

# installs SvelteKit with changes from this PR
npm i -D https://pkg.pr.new/sveltejs/kit/@sveltejs/kit@27e37ab

Any feedback is welcome.

[dummdidumm]

nice!

[onesinghashish]

@eltigerchino thanks for the fix. eagerly waiting for the release :)

You can try it out right now while waiting for the official release. Just run:

# installs SvelteKit with changes from this PR
npm i -D https://pkg.pr.new/sveltejs/kit/@sveltejs/kit@27e37ab

Any feedback is welcome.

@eltigerchino works great. thanks