Document how to cache @sveltejs/enhanced-img in GitHub Pages

[janosh]

Describe the problem

i have a site build that went from 1 min on build and deploy with https://github.com/actions/deploy-pages to 11 min after adding @sveltejs/enhanced-img. locally, this is a 1 time cost since the transformed images are cached in node_modules. caching does not work out of the box in CI though. since this seems like a very common use case, i think it makes sense to recommend this to users and show them how to do it

Describe the proposed solution

https://svelte.dev/docs/kit/images seems like a good place to document how to cache @sveltejs/enhanced-img in GitHub actions.

another option to speed up builds would be to allow configuring which image formats to build. e.g. i only really need PNG to Avif conversion, but there's no way to configure that. related issue tracking the ability to pass vite-imagetools config: #12615

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response