fix: add typing to CSSOptions.preprocessorOptions

[alex-kinokon]

Description

Fixes #17984. This adds optional type definition to CSSOptions.preprocessorOptions. Users who have installed sass will see the correct types, while others will simply see it as any:

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[sapphi-red]

Thanks! I added types for less and stylus and resolved the conflict.

I tested the built package with create-vite and it worked as expected.

[patak-dev]

/ecosystem-ci run

[vite-ecosystem-ci]

📝 Ran ecosystem CI on 208daa2: Open

suite	result	latest scheduled
analogjs	❌ failure	❌ failure
histoire	❌ failure	❌ failure
remix	❌ failure	❌ failure
sveltekit	❌ failure	❌ failure
vike	❌ failure	❌ failure

✅ astro, ladle, laravel, marko, nuxt, previewjs, quasar, qwik, rakkas, redwoodjs, storybook, unocss, vite-environment-examples, vite-plugin-pwa, vite-plugin-react, vite-plugin-react-swc, vite-plugin-svelte, vite-plugin-vue, vite-setup-catalogue, vitepress, vitest, vuepress

[hi-ogawa]

Speaking of optional peer deps, it looks like currently lightningcss typing is partially bundled (maybe this is related? #14209). Perhaps, this could be also externalized with @ts-ignore? (not in this PR, but maybe later)

[sapphi-red]

@hi-ogawa Yeah, I think we can do this for lightningcss too.

[bluwy]

Thanks for finishing this up sapphi!