build: update dependencies

- build with flutter 3.7
- fix lint infos

Author: deandreamatias

example/lib/main.dart

@@ -32,10 +32,10 @@ class MyHomePage extends StatefulWidget {
   const MyHomePage({Key? key}) : super(key: key);
 
   @override
-  _MyHomePageState createState() => _MyHomePageState();
+  MyHomePageState createState() => MyHomePageState();
 }
 
-class _MyHomePageState extends State<MyHomePage> {
+class MyHomePageState extends State<MyHomePage> {
   final _formKey = GlobalKey<FormBuilderState>();
 
   void _onChanged(dynamic val) => debugPrint(val.toString());