Bump html-proofer from 3.19.4 to 4.2.0

Bumps [html-proofer](https://github.com/gjtorikian/html-proofer) from 3.19.4 to 4.2.0.
- [Release notes](https://github.com/gjtorikian/html-proofer/releases)
- [Changelog](https://github.com/gjtorikian/html-proofer/blob/main/CHANGELOG.md)
- [Commits](https://github.com/gjtorikian/html-proofer/compare/v3.19.4...v4.2.0)

---
updated-dependencies:
- dependency-name: html-proofer
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -77,7 +77,7 @@ GEM
     html-pipeline (2.13.0)
       activesupport (>= 2)
       nokogiri (>= 1.4)
-    html-proofer (3.19.4)
+    html-proofer (4.2.0)
       addressable (~> 2.3)
       mercenary (~> 0.3)
       nokogiri (~> 1.13)
@@ -85,6 +85,7 @@ GEM
       rainbow (~> 3.0)
       typhoeus (~> 1.3)
       yell (~> 2.0)
+      zeitwerk (~> 2.5)
     http_parser.rb (0.8.0)
     i18n (1.10.0)
       concurrent-ruby (~> 1.0)