feat: add file to run minimal code example

Author: deandreamatias

example/lib/minimal_code_example.dart

@@ -0,0 +1,64 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_form_builder/flutter_form_builder.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:form_builder_validators/form_builder_validators.dart';
+
+void main() => runApp(const MyApp());
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Flutter FormBuilder Example',
+      debugShowCheckedModeBanner: false,
+      localizationsDelegates: const [
+        FormBuilderLocalizations.delegate,
+        ...GlobalMaterialLocalizations.delegates,
+        GlobalWidgetsLocalizations.delegate,
+      ],
+      supportedLocales: FormBuilderLocalizations.supportedLocales,
+      home: const _ExamplePage(),
+    );
+  }
+}
+
+class _ExamplePage extends StatefulWidget {
+  const _ExamplePage();
+
+  @override
+  State<_ExamplePage> createState() => _ExamplePageState();
+}
+
+class _ExamplePageState extends State<_ExamplePage> {
+  final _formKey = GlobalKey<FormBuilderState>();
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: FormBuilder(
+        key: _formKey,
+        child: Column(
+          children: [
+            FormBuilderTextField(
+              name: 'full_name',
+              decoration: const InputDecoration(labelText: 'Full Name'),
+              validator: FormBuilderValidators.compose([
+                FormBuilderValidators.required(),
+              ]),
+            ),
+            const SizedBox(height: 10),
+            ElevatedButton(
+              onPressed: () {
+                _formKey.currentState?.saveAndValidate();
+                debugPrint(_formKey.currentState?.value.toString());
+              },
+              child: const Text('Print'),
+            )
+          ],
+        ),
+      ),
+    );
+  }
+}