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/diagnostic/index.ts

@@ -41,7 +41,9 @@ import { Cordova, CordovaProperty, IonicNativePlugin, Plugin } from '@ionic-nati
   repo: 'https://github.com/dpa99c/cordova-diagnostic-plugin',
   platforms: ['Android', 'iOS', 'Windows']
 })
-@Injectable()
+@Injectable({
+  providedIn: 'root'
+})
 export class Diagnostic extends IonicNativePlugin {
   permission = {
     READ_CALENDAR: 'READ_CALENDAR',