chore(docs): Add meta reducers injection in the Store docs (#341)

Author: laurentgoudet

docs/store/README.md

@@ -117,6 +117,7 @@ export class MyAppComponent {
 - [Action Reducers](./actions.md#action-reducers)
 - [Injecting reducers](./api.md#injecting-reducers)
 - [Meta-Reducers/Enhancers](./api.md#meta-reducers)
+- [Injecting Meta-Reducers](./api.md#injecting-meta-reducers)
 - [Providing initial state](./api.md#initial-state)
 - [State composition through feature modules](./api.md#feature-module-state-composition)
 - [State selectors](./selectors.md)

docs/store/api.md

@@ -158,3 +158,29 @@ export const reducers: ActionReducerMap<fromFeature.State> = {
 })
 export class FeatureModule { }
 ```
+
+## Injecting Meta-Reducers
+
+To inject meta reducers, use the `META_REDUCERS` injection token exported in
+the Store API and a `Provider` to register the meta reducers through dependency
+injection.
+
+```
+import { MetaReducer, META_REDUCERS } '@ngrx/store';
+import { SomeService } from './some.service';
+
+export function getMetaReducers(some: SomeService): MetaReducer[] {
+  // return array of meta reducers;
+}
+
+@NgModule({
+  providers: [
+    {
+      provide: META_REDUCERS,
+      deps: [SomeService],
+      useFactory: getMetaReducers
+    }
+  ]
+})
+export class AppModule {}
+```