Display subcategory part count

lib/inventree/part.dart

@@ -14,6 +14,8 @@ class InvenTreePartCategory extends InvenTreeModel {
 
   String get pathstring => jsondata['pathstring'] ?? '';
 
+  int get partcount => jsondata['parts'] ?? 0;
+
   InvenTreePartCategory() : super();
 
   InvenTreePartCategory.fromJson(Map<String, dynamic> json) : super.fromJson(json) {

lib/widget/category_display.dart

@@ -202,6 +202,7 @@ class SubcategoryList extends StatelessWidget {
     return ListTile(
       title: Text("${cat.name}"),
       subtitle: Text("${cat.description}"),
+      trailing: Text("${cat.partcount}"),
       onTap: () {
         _openCategory(context, cat.pk);
       }