Add hook for entity list builder

Seems #9 has been committed and no follow up to this so going to close for now. If still valid please reopen.

I came here looking for how to override an entity list builder class, which is done with hook_entity_type_alter()
(see https://drupal.stackexchange.com/questions/191508/can-you-change-the-lis...)
which will then allow you to override the methods mentioned in previous comments