refactor: optimize plugins for angular treeshaking

BREAKING CHANGE: You can remove the plugin import from the app.module.ts because of the changed Inject decorator

src/@ionic-native/plugins/appodeal/index.ts

@@ -27,7 +27,9 @@ import { Observable } from 'rxjs';
   repo: 'https://github.com/appodeal/appodeal-cordova-plugin',
   platforms: ['iOS', 'Android']
 })
-@Injectable()
+@Injectable({
+  providedIn: 'root'
+})
 export class Appodeal extends IonicNativePlugin {
   // available types of advertisements
   readonly AD_TYPES = {