Add note on reducer/dispatcher power feature.

Author: ghengeveld

README.md

@@ -377,8 +377,14 @@ Callback function invoked when a promise rejects, receives rejection reason (err
 
 > `function(state: any, action: Object, internalReducer: function(state: any, action: Object))`
 
-State reducer to take full control over state updates by wrapping the internal reducer. It receives the current state,
-the dispatched action and the internal reducer. You probably want to invoke the internal reducer at some point.
+State reducer to take full control over state updates by wrapping the [internal reducer]. It receives the current
+state, the dispatched action and the internal reducer. You probably want to invoke the internal reducer at some point.
+
+> This is a power feature which loosely follows the [state reducer pattern]. It allows you to control state changes by
+> intercepting actions before they are handled, or by overriding or enhancing the reducer itself.
+
+[internal reducer]: https://github.com/ghengeveld/react-async/blob/master/src/reducer.js
+[state reducer pattern]: https://kentcdodds.com/blog/the-state-reducer-pattern
 
 #### `dispatcher`
 
@@ -388,6 +394,9 @@ Action dispatcher to take full control over action dispatching by wrapping the i
 original action, the internal dispatcher and all component props (or options). You probably want to invoke the internal
 dispatcher at some point.
 
+> This is a power feature similar to the [state reducer pattern]. It allows you to control state changes by
+> intercepting actions before they are dispatched, to dispatch additional actions, possibly later in time.
+
 #### `defer`
 
 > `boolean`