title: No provider for HttpHandler with ngrx/effects
body: <p>I'm trying to recreate an authEffect very similar to the <a href="https://github.com/ngrx/platform/tree/master/docs/effects" rel="noreferrer">ngrx docs</a>, and getting this error message: 
  <code>Error: StaticInjectorError(AppModule)[HttpClient -&gt; HttpHandler]: 
    StaticInjectorError(Platform: core)[HttpClient -&gt; HttpHandler]: 
      NullInjectorError: No provider for HttpHandler!</code></p>
  
  <p>the effect service: </p>
  
  <pre><code>@Injectable()
  export class HttpEffects {
    constructor(private http: HttpClient, private actions$: Actions) {}
  
    @Effect() login$: Observable&lt;ActionWithPayload&gt; = this.actions$.pipe(
      ofType(ActionTypes.SEND_LOGIN),
      mergeMap((action: ActionWithPayload) =&gt;
        this.http.post(SERVER_URL + LOGINAPI.LOGIN, action.payload, config).pipe(
          map(data =&gt; ({type: 'LOGIN_SUCCESS', payload: data})),
          catchError(() =&gt; of({type: 'LOGIN_ERROR'}))
        ))
    );
  }
  </code></pre>
  
  <p>app.module:</p>
  
  <pre><code>@NgModule({
    declarations: [
      AppComponent,
    ],
    imports: [
      BrowserModule,
      BrowserAnimationsModule,
      StoreModule.forRoot(rootReducer),
      StoreDevtoolsModule.instrument({
        maxAge: 10
      }),
      EffectsModule.forRoot([HttpEffects])
    ],
    exports: [
      BrowserAnimationsModule
    ],
    providers: [ HttpClient ],
    bootstrap: [AppComponent]
  })
  </code></pre>
  
  <p>I've tried to import the effect service in a feature model as well, with <code>EffectsModule.forFeature()</code>, but the same error is thrown.</p>