Make syntect fancy

[cuviper]

This switches syntect from onig to fancy-regex for a pure Rust
implementation of regular expressions.

It's also worth noting that onig's underlying oniguruma library says
"This project ended on April 24, 2025", with its repo archived.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[cuviper]

I don't know that I care to deal with a CLA for such a small change. I welcome anyone else to recreate this, which should be trivial even without looking at my commit.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.68%. Comparing base (886f15e) to head (16df8c1).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #265      +/-   ##
==========================================
+ Coverage   84.74%   85.68%   +0.93%     
==========================================
  Files          15       17       +2     
  Lines        3377     3674     +297     
  Branches     3377     3674     +297     
==========================================
+ Hits         2862     3148     +286     
- Misses        413      423      +10     
- Partials      102      103       +1     

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[mgeisler]

I don't know that I care to deal with a CLA for such a small change. I welcome anyone else to recreate this, which should be trivial even without looking at my commit.

Yeah, I understand completely! Sorry for the speed bump, it's a Google-wide policy to require an explicit signoff via the CLA.

I'll recreate it like you suggest. Thanks for the PR!

[mgeisler]

#267 should do the same, thanks again!