Render rdoc code example for routing defaults method

Author: mjankowski

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -1053,6 +1053,7 @@ def constraints(constraints = {}, &block)
         end
 
         # Allows you to set default parameters for a route, such as this:
+        #
         #     defaults id: 'home' do
         #       match 'scoped_pages/(:id)', to: 'pages#show'
         #     end