First fixed

config/environments/development.rb

@@ -9,6 +9,9 @@ Rails.application.configure do
   # Do not eager load code on boot.
   config.eager_load = false
 
+  config.public_file_server.enabled   = true
+  config.public_file_server.headers = { 'Cache-Control' => 'public, max-age=3600' }
+
   # Show full error reports and disable caching.
   config.consider_all_requests_local       = true
   config.action_controller.perform_caching = false