build this page to allow adding devices

https://api.github.com/ammaratef45/hydroponics-garden/blob/dd063bd50cabd7f815bd0d12cf0037e4c76ce144/lib/widgets/devices_widget.dart#L9

```dart

import 'package:flutter/material.dart';
import 'package:hydroponic_garden/widgets/main_widget.dart';

class DevicesPage extends StatelessWidget {
const DevicesPage({super.key});

@override
Widget build(BuildContext context) {
// TODO build this page to allow adding devices
// TODO added devices should show a snapshot of device status
// TODO when an added device is clicked it should navigate to device_widget
return const MainWidget(
body: Center(
child: Text('placeholder'),
),
);
}
}

```