model: Add GlobalLocalizations class for static access to localizations

Author: sirpengi

lib/model/localizations.dart

@@ -0,0 +1,6 @@
+import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
+
+abstract final class GlobalLocalizations {
+  static ZulipLocalizations zulipLocalizations =
+    lookupZulipLocalizations(ZulipLocalizations.supportedLocales.first);
+}

lib/widgets/app.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 
+import '../model/localizations.dart';
 import '../model/narrow.dart';
 import 'about_zulip.dart';
 import 'login.dart';
@@ -49,6 +50,10 @@ class ZulipApp extends StatelessWidget {
         localizationsDelegates: ZulipLocalizations.localizationsDelegates,
         supportedLocales: ZulipLocalizations.supportedLocales,
         theme: theme,
+        builder: (BuildContext context, Widget? child) {
+          GlobalLocalizations.zulipLocalizations = ZulipLocalizations.of(context);
+          return child!;
+        },
         home: const ChooseAccountPage()));
   }
 }