feat: add @shikijs/twoslash-unocss package

[khushthecoder]

• [x]

Description

This PR adds a new UnoCSS-backed twoslash runner that resolves utility classes to their generated CSS and surfaces them as hover information in Shiki code blocks.

The goal is to provide UnoCSS utility hover support similar to how twoslash works for TypeScript. When hovering over a utility class inside a code block, the generated CSS is displayed inline via the twoslash hover protocol.

A new package @shikijs/twoslash-unocss is introduced. The implementation follows the twoslash-eslint pattern discussed in the issue. It:

• Tokenizes the input code
• Extracts potential UnoCSS utility class names
• Uses @unocss/core's createGenerator to generate CSS
• Returns NodeHover nodes via the twoslash protocol

Since UnoCSS v0.65+ is fully async (generator creation and CSS generation), the twoslasher function itself is async. createTransformerFactory handles the returned Promise internally, so no manual pre-resolution is required by users.

Tests included:

• Single class resolution
• Multiple class resolution
• Unknown class handling
• Position accuracy
• Empty input
• Multiline support

All tests pass.

Linked Issues

fixes #794

Additional context

Reviewers may want to focus on:

• Hover position mapping accuracy
• Performance implications of async generation
• Preset configuration ergonomics, especially whether the config API feels natural compared to how UnoCSS is typically configured elsewhere
• Overall API design consistency with existing twoslash integrations

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[codecov]

Codecov Report

❌ Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.61%. Comparing base (ae3553d) to head (6c9cae0).

Files with missing lines	Patch %	Lines
packages/twoslash-unocss/src/index.ts	97.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1256      +/-   ##
==========================================
+ Coverage   89.53%   89.61%   +0.07%     
==========================================
  Files          79       80       +1     
  Lines        3479     3514      +35     
  Branches     1009     1016       +7     
==========================================
+ Hits         3115     3149      +34     
- Misses        328      329       +1     
  Partials       36       36              

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[antfu]

Thanks for the PR! But I think this would be better to live in Uno's repo instead. Could you reopen a new PR there? Thanks