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/barcode-scanner/index.ts

@@ -108,7 +108,9 @@ export interface BarcodeScanResult {
   repo: 'https://github.com/phonegap/phonegap-plugin-barcodescanner',
   platforms: ['Android', 'BlackBerry 10', 'Browser', 'iOS', 'Windows']
 })
-@Injectable()
+@Injectable({
+  providedIn: 'root'
+})
 export class BarcodeScanner extends IonicNativePlugin {
   Encode: {
     TEXT_TYPE: string;