Add an example to the repo

This adds an example to the repo

[changelog]
added: Added an example directory to include a quick example to be displayed on pub.dev

example/main.dart

@@ -0,0 +1,47 @@
+import 'package:appfit/appfit.dart';
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(const MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return const MaterialApp(
+      title: 'AppFit Example',
+      home: AppFitExample(),
+    );
+  }
+}
+
+class AppFitExample extends StatefulWidget {
+  const AppFitExample({super.key});
+
+  @override
+  AppFitExampleState createState() => AppFitExampleState();
+}
+
+class AppFitExampleState extends State<AppFitExample> {
+  final appFit = AppFit(configuration: AppFitConfiguration(apiKey: "API_KEY"));
+
+  @override
+  void initState() {
+    super.initState();
+    appFit.trackEvent('screen_name', properties: {'name': 'AppFit Example'});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('AppFit Example'),
+      ),
+      body: const Center(
+        child: Text("Welcome to the AppFit example app."),
+      ),
+    );
+  }
+}