Implemented inbox (still WIP)

lib/core/model/paperless_statistics_state.dart

@@ -0,0 +1,11 @@
+import 'package:paperless_mobile/core/model/paperless_statistics.dart';
+
+class PaperlessStatisticsState {
+  final bool isLoaded;
+  final PaperlessStatistics? statistics;
+
+  PaperlessStatisticsState({
+    required this.isLoaded,
+    this.statistics,
+  });
+}