added storage dependencies in app module

src/app/app.module.ts

+// ionic native dependencies
 import { NgModule } from '@angular/core';
 import { BrowserModule } from '@angular/platform-browser';
 import { RouteReuseStrategy } from '@angular/router';
+import { HttpClientModule } from '@angular/common/http';
 
+// ionic native dependencies
 import { IonicModule, IonicRouteStrategy } from '@ionic/angular';
 import { SplashScreen } from '@ionic-native/splash-screen/ngx';
 import { StatusBar } from '@ionic-native/status-bar/ngx';
+import { Geolocation } from '@ionic-native/geolocation/ngx';
+import { IonicStorageModule } from '@ionic/storage';
 
+// custom dependencies
 import { AppComponent } from './app.component';
 import { AppRoutingModule } from './app-routing.module';
-import { Geolocation } from '@ionic-native/geolocation/ngx';
-
-import { HttpClientModule } from '@angular/common/http';
-
 import { RestService } from './rest.service';
 
 @NgModule({
@@ -21,7 +23,8 @@ import { RestService } from './rest.service';
     BrowserModule,
     HttpClientModule,
     IonicModule.forRoot(),
-    AppRoutingModule
+    AppRoutingModule,
+    IonicStorageModule.forRoot()
   ],
   providers: [
     Geolocation,