DEV: Add site description to crawler homepage view (#32845)

In some cases, Google crawlers don't output the meta description but
rather they output the first bit of text in the UI. Sometimes that is a
mix of table headings, topic titles and excerpts, which don't reflect
the site's mission. Adding the description to the homepage header might
help.

Internal ticket t/154372

app/controllers/application_controller.rb

@@ -80,6 +80,7 @@ class ApplicationController < ActionController::Base
             CrawlerDetection.crawler?(request.user_agent, request.headers["HTTP_VIA"])
         )
   end
+  helper_method :use_crawler_layout?
 
   def perform_refresh_session
     refresh_session(current_user) unless @readonly_mode