Bump github.com/alecthomas/chroma/v2 from 2.20.0 to 2.21.1 (#582)

Bumps [github.com/alecthomas/chroma/v2](https://github.com/alecthomas/chroma) from 2.20.0 to 2.21.1.
- [Release notes](https://github.com/alecthomas/chroma/releases)
- [Commits](https://github.com/alecthomas/chroma/compare/v2.20.0...v2.21.1)

---
updated-dependencies:
- dependency-name: github.com/alecthomas/chroma/v2
  dependency-version: 2.21.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -4,7 +4,7 @@ go 1.25.1
 
 require (
 	github.com/Kunde21/markdownfmt/v3 v3.1.0
-	github.com/alecthomas/chroma/v2 v2.20.0
+	github.com/alecthomas/chroma/v2 v2.21.1
 	github.com/blevesearch/bleve/v2 v2.5.7
 	github.com/dustin/go-humanize v1.0.1
 	github.com/gabriel-vasile/mimetype v1.4.12