chore: Introduce the NotImplementedDialog (#70)

Author: nivisi

lib/presentation/utils/not_implemented_dialog/not_implemented_dialog.dart

@@ -0,0 +1,41 @@
+import 'package:flutter/material.dart';
+
+/// A very simple dialog to indicate that something was not implemented yet.
+///
+/// Show it like this:
+/// ```dart
+/// onPressed: () {
+///   NotImplementedDialog.show(context);
+///   // Or:
+///   context.notImplementedYet();
+/// },
+/// ```
+class NotImplementedDialog extends StatelessWidget {
+  const NotImplementedDialog._({Key? key}) : super(key: key);
+
+  static Future<void> show(BuildContext context) {
+    return showDialog(
+      context: context,
+      builder: (context) => const NotImplementedDialog._(),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AlertDialog(
+      title: const Text('Not implemented yet'),
+      content: const Text('This was not implemented yet!'),
+      actions: [
+        TextButton(
+          onPressed: Navigator.of(context).pop,
+          child: const Text('OK'),
+        )
+      ],
+    );
+  }
+}
+
+extension NotImplementedDialogBuildContextExtension on BuildContext {
+  /// Displays a [NotImplementedDialog].
+  Future<void> notImplementedYet() => NotImplementedDialog.show(this);
+}