New Example - Platform Adaptive Example (#121)

* Adding Platform Adaptive Example

* Adding screenshots

using_platform_adaptive/lib/common_widgets/adaptive_button.dart

@@ -0,0 +1,34 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:using_platform_adaptive/platform_adaptive.dart';
+
+class AdaptiveButton extends PlatformAdaptiveWidget {
+  const AdaptiveButton(
+      {super.forcePlatform,
+      this.color,
+      required this.child,
+      this.onPressed,
+      super.key});
+
+  final void Function()? onPressed;
+  final Widget child;
+  final Color? color;
+
+  @override
+  Widget buildAndroid(BuildContext context) {
+    return MaterialButton(
+      onPressed: onPressed,
+      color: color,
+      child: child,
+    );
+  }
+
+  @override
+  Widget buildIOS(BuildContext context) {
+    return CupertinoButton(
+      onPressed: onPressed,
+      color: color,
+      child: child,
+    );
+  }
+}