Warn in Readme that configuration should not go into `config/initiali…

…zers/*.rb`

README.md

@@ -212,7 +212,11 @@ to delete old records and preserve space in your database.
 
 To use GoodJob, you can set `config.active_job.queue_adapter` to a `:good_job`.
 
-Additional configuration can be provided via `config.good_job.OPTION = ...` for example:
+Additional configuration can be provided via `config.good_job.OPTION = ...`.
+
+_Configuration **must** be placed into `config/application.rb` or `config/environments/{RAILS_ENV}.rb`; configuration may not work correctly if placed into `config/initializers/*.rb` because application initializers run _after_ gem initialization (see [Rails#36650](https://github.com/rails/rails/issues/36650) and [GoodJob#380](https://github.com/bensheldon/good_job/issues/380))._
+
+Configuration examples:
 
 ```ruby
 # config/application.rb