Merge branch 'bw-banzai-task' into 'master'

Add rake task for easier Banzai render testing

See merge request gitlab-org/gitlab!79248

lib/tasks/gitlab/banzai.rake

+# frozen_string_literal: true
+
+namespace :gitlab do
+  namespace :banzai do
+    desc 'GitLab | Banzai | Render markdown using our FullPipeline (input will be requested)'
+    task render: :environment do |_t|
+      markdown = []
+
+      puts "\nEnter markdown below, Ctrl-D to end (if you need blank lines, paste in the full text):"
+      while buf = Readline.readline('', true)
+        markdown << buf
+      end
+
+      puts "Rendering using Gitlab's FullPipeline...\n\n"
+
+      html = MarkupHelper.markdown(markdown.join("\n"), { pipeline: :full, project: nil })
+      puts html.gsub('&#x000A;', "\n")
+    end
+  end
+end