add timeline pkg to flutter

packages/z-timeline/lib/state.dart

@@ -0,0 +1,82 @@
+class TimelineState {
+  final TimelineData timeline;
+  final String? selectedItemId;
+
+  TimelineState({required this.timeline, this.selectedItemId});
+
+  factory TimelineState.fromJson(Map<String, dynamic> json) {
+    return TimelineState(
+      timeline: TimelineData.fromJson(json['timeline'] as Map<String, dynamic>),
+      selectedItemId: json['selectedItemId'] as String?,
+    );
+  }
+}
+
+class TimelineData {
+  final String id;
+  final String title;
+  final List<TimelineGroupData> groups;
+
+  TimelineData({required this.id, required this.title, required this.groups});
+
+  factory TimelineData.fromJson(Map<String, dynamic> json) {
+    return TimelineData(
+      id: json['id'] as String,
+      title: json['title'] as String,
+      groups: (json['groups'] as List<dynamic>)
+          .map((g) => TimelineGroupData.fromJson(g as Map<String, dynamic>))
+          .toList(),
+    );
+  }
+}
+
+class TimelineGroupData {
+  final String id;
+  final String title;
+  final int sortOrder;
+  final List<TimelineItemData> items;
+
+  TimelineGroupData({
+    required this.id,
+    required this.title,
+    required this.sortOrder,
+    required this.items,
+  });
+
+  factory TimelineGroupData.fromJson(Map<String, dynamic> json) {
+    return TimelineGroupData(
+      id: json['id'] as String,
+      title: json['title'] as String,
+      sortOrder: json['sortOrder'] as int,
+      items: (json['items'] as List<dynamic>)
+          .map((i) => TimelineItemData.fromJson(i as Map<String, dynamic>))
+          .toList(),
+    );
+  }
+}
+
+class TimelineItemData {
+  final String id;
+  final String title;
+  final String? description;
+  final String start;
+  final String? end;
+
+  TimelineItemData({
+    required this.id,
+    required this.title,
+    this.description,
+    required this.start,
+    this.end,
+  });
+
+  factory TimelineItemData.fromJson(Map<String, dynamic> json) {
+    return TimelineItemData(
+      id: json['id'] as String,
+      title: json['title'] as String,
+      description: json['description'] as String?,
+      start: json['start'] as String,
+      end: json['end'] as String?,
+    );
+  }
+}