feat(transformers): support word highlighting across multiple tokens

[fuma-nama]

Support word highlighting across multiple tokens. To be precise, it finds all matching words in the line and highlights them individually.

• Add a test if possible
• Format all commit messages with Conventional Commits

• This PR fixes transformerMetaWordHighlight highlight is not working when word includes symbols antfu/shikiji#110

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[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (9504c7f) 97.07% compared to head (110df7f) 97.05%.

Files	Patch %	Lines
packages/transformers/src/shared/highlight-word.ts	97.18%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #561      +/-   ##
==========================================
- Coverage   97.07%   97.05%   -0.02%     
==========================================
  Files          54       54              
  Lines        5027     5066      +39     
  Branches      648      656       +8     
==========================================
+ Hits         4880     4917      +37     
- Misses        143      145       +2     
  Partials        4        4              

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