Split code into three Dart files

This follows recommendations [1] from the flutter documentation.

[1]: https://docs.flutter.dev/app-architecture/concepts

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/data.dart b/lib/data.dart
new file mode 100644
index 0000000..f2e3531
--- /dev/null
+++ b/lib/data.dart
@@ -0,0 +1,6 @@
+class Contact {
+  final String address;
+  bool isOpen;
+
+  Contact({required this.address, required this.isOpen});
+}