Add a rake task `benchmark:banzai`

lib/tasks/benchmark.rake

+# frozen_string_literal: true
+
+return if Rails.env.production?
+
+namespace :benchmark do
+  desc 'Benchmark | Banzai pipeline/filters'
+  RSpec::Core::RakeTask.new(:banzai) do |t|
+    t.pattern = 'spec/benchmarks/banzai_benchmark.rb'
+    ENV['BENCHMARK'] = '1'
+  end
+end

spec/benchmarks/banzai_benchmark.rb

@@ -12,6 +12,8 @@ if ENV.key?('BENCHMARK')
   #
   # Run by:
   #   BENCHMARK=1 rspec spec/benchmarks/banzai_benchmark.rb
+  # or
+  #   rake benchmark:banzai
   #
   RSpec.describe 'GitLab Markdown Benchmark', :aggregate_failures do
     include MarkupHelper