Add support for ads.txt redirect

plugin.rb

@@ -176,3 +176,20 @@ and (max-width : 775px) {
 }
 
 CSS
+
+after_initialize do
+  require_dependency 'application_controller'
+  class ::AdstxtController < ::ApplicationController
+    skip_before_action :check_xhr
+
+    def index
+      raise Discourse::NotFound unless SiteSetting.adsense_ads_txt_url.present?
+
+      redirect_to SiteSetting.adsense_ads_txt_url
+    end
+  end
+
+  Discourse::Application.routes.append do
+    get '/ads.txt' => "adstxt#index"
+  end
+end