fix: Fix build with newer versions of Flutter

lib/src/data/manga.g.dart

@@ -6,19 +6,21 @@ part of 'manga.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-_$_MangaTrackingData _$$_MangaTrackingDataFromJson(Map<String, dynamic> json) =>
-    _$_MangaTrackingData(
+_$MangaTrackingDataImpl _$$MangaTrackingDataImplFromJson(
+        Map<String, dynamic> json) =>
+    _$MangaTrackingDataImpl(
       json['id'] as String,
-      const MediumTrackingStateConverter().fromJson(json['state'] as int),
+      const MediumTrackingStateConverter()
+          .fromJson((json['state'] as num).toInt()),
       json['title'] as String,
-      json['chaptersRead'] as int,
-      json['volumesOwned'] as int,
-      json['chaptersTotal'] as int?,
+      (json['chaptersRead'] as num).toInt(),
+      (json['volumesOwned'] as num).toInt(),
+      (json['chaptersTotal'] as num?)?.toInt(),
       json['thumbnailUrl'] as String,
     );
 
-Map<String, dynamic> _$$_MangaTrackingDataToJson(
-        _$_MangaTrackingData instance) =>
+Map<String, dynamic> _$$MangaTrackingDataImplToJson(
+        _$MangaTrackingDataImpl instance) =>
     <String, dynamic>{
       'id': instance.id,
       'state': const MediumTrackingStateConverter().toJson(instance.state),