title: How to implement customReducer in React-Admin
body: <p>I try to implement a customReducer to manage my own custom state in React-Admin. I have looked through the documentation. I can see where to register the reducer in the <code>&lt;Admin&gt;</code>, but I don't see where to really <strong>dispatch</strong> the reducer to store the state.</p>
  <p>I also wish to know how to <strong>retrieve</strong> my state from the Redux store. What dataProvider is appropriate for this?</p>
  <p>Please could someone share a code snippet to do this?</p>
  <p>Thanks</p>