Translation fix (#424)

* Fix locale header

- Moving to new framework meant that Intl.getCurrentLocale was no longer working

* Update release notes

* Fix typo in pubspec.yaml

* Clear cached values when locale is changed

* Add extra context check

lib/main.dart

@@ -152,6 +152,8 @@ class InvenTreeAppState extends State<StatefulWidget> {
     });
   }
 
+  Locale? get locale => _locale;
+
   @override
   Widget build(BuildContext context) {