Added fskg category

[slavvka]

fixes #48

[Hanh94]

Hi @slavvka, Thank you very much for your kind feedback.
We think of this as a switch category
Just need to add the following code:

  case 'kg':
  case 'tdq':
  case 'fskg':
        var deviceData = new DataUtil().getSubService(device.status)
        deviceAccessory = new SwitchAccessory(this, homebridgeAccessory, device, deviceData);
        this.accessories.set(uuid, deviceAccessory.homebridgeAccessory);
        this.deviceAccessories.set(uuid, deviceAccessory);
        break;