Vite: Support Tailwind in Svelte <style> blocks

[philipp-spiess]

Closes #13305

This PR adds registers a Svelte preprocessor, used by the Svelte Vite plugin, to run Tailwind CSS for styles inside the <style> block, this enables users to use Tailwind CSS features like @apply from inside Svelte components:

<script>
  let name = 'world'
</script>
<h1 class="foo underline">Hello {name}!</h1>
<style global>
  @import 'tailwindcss/utilities';
  @import 'tailwindcss/theme' theme(reference);
  @import './components.css';
</style>

Test Plan

I've added integration tests to validate this works as expected. Furthermore I've used the tailwindcss-playgrounds SvelteKit project to ensure this works in an end-to-end setup: