subscription_list: Fix stream name sorting case insensitively

Stream names should be sorted regardless of the case and this
applies for pinned and unpinned subscriptions:
**A comes before b and B comes after a**

So this adds simple toLowerCase transformation before sorting

Fixes: #568

Author: Khader-1

lib/widgets/subscription_list.dart

@@ -77,8 +77,8 @@ class _SubscriptionListPageState extends State<SubscriptionListPage> with PerAcc
       }
     }
     // TODO(i18n): add locale-aware sorting
-    pinned.sortBy((subscription) => subscription.name);
-    unpinned.sortBy((subscription) => subscription.name);
+    pinned.sortBy((subscription) => subscription.name.toLowerCase());
+    unpinned.sortBy((subscription) => subscription.name.toLowerCase());
 
     return Scaffold(
       appBar: AppBar(title: const Text("Streams")),

test/widgets/subscription_list_test.dart

@@ -120,6 +120,18 @@ void main() {
       ]);
       check(listedStreamIds(tester)).deepEquals([2, 3, 1]);
     });
+
+    testWidgets('subscriptions sorting is case insensitive', (tester) async {
+      await setupStreamListPage(tester, subscriptions: [
+        eg.subscription(eg.stream(streamId: 1, name: 'a'), pinToTop: true),
+        eg.subscription(eg.stream(streamId: 2, name: 'B'), pinToTop: true),
+        eg.subscription(eg.stream(streamId: 3, name: 'c'), pinToTop: true),
+        eg.subscription(eg.stream(streamId: 4, name: 'D'), pinToTop: false),
+        eg.subscription(eg.stream(streamId: 5, name: 'e'), pinToTop: false),
+        eg.subscription(eg.stream(streamId: 6, name: 'F'), pinToTop: false),
+      ]);
+      check(listedStreamIds(tester)).deepEquals([1, 2, 3, 4, 5, 6]);
+    });
   });
 
   testWidgets('unread badge shows with unreads', (tester) async {