Merge branch 'enable-markup-highlighting' into 'master'

Add SyntaxHighlightFilter to markup pipeline

Closes #20023

See merge request gitlab-org/gitlab-ce!25761

changelogs/unreleased/enable-markup-highlighting.yml

+---
+title: Enable syntax highlighting to other supported markups
+merge_request: 25761
+author:
+type: other

lib/banzai/pipeline/markup_pipeline.rb

@@ -7,7 +7,8 @@ module Banzai
         @filters ||= FilterArray[
           Filter::SanitizationFilter,
           Filter::ExternalLinkFilter,
-          Filter::PlantumlFilter
+          Filter::PlantumlFilter,
+          Filter::SyntaxHighlightFilter
         ]
       end
     end