Refactor ElectronService.runningInElectron

[ThorstenHans]

Had selected a bad naming for this one. It's also not that intuitive to have it only as static property on ElectronService.

Refactor it to

ElectronService.isElectronApp and add an additional instance property.

Developers should be able to access it also on an existing instance of ElectronService, that may be a bit more self-explaining.

@Component({})
export class MyComp implements OnInit {

  constructor(private _electronService: ElectronService) { }
 
  public ngOnInit(): void {
    if(this._electronService.isElectronApp) {
      // whatever
    }
  }
}