Set device name to "Nexus on $platform"

Fixes #86.

.gitmodules

@@ -1,4 +1,4 @@
 [submodule "gomuks"]
 	path = gomuks
 	url = https://github.com/Henry-Hiles/gomuks
-	branch = quad/chore/remove-root-set
+	branch = quad/feat/customizable-device-name

gomuks

@@ -1 +1 @@
-Subproject commit c20070298d450cc02f465a503a5a52fea74af0d5
+Subproject commit ae11daa1b14b103688e57accb9c65ad6401cb3ef

lib/controllers/client.dart

@@ -7,6 +7,7 @@ import "dart:math";
 import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:ffi/ffi.dart";
 import "package:flutter/foundation.dart";
+import "package:intl/intl.dart";
 import "package:nexus/controllers/account_data.dart";
 import "package:nexus/controllers/client_state.dart";
 import "package:nexus/controllers/init_complete.dart";
@@ -68,7 +69,17 @@ class ClientController extends AsyncNotifier<int> {
           ..free(valuePtr);
       }
     }
-    final handle = await Isolate.run(GomuksInit);
+    final handle = await Isolate.run(() {
+      final message =
+          "Nexus on ${toBeginningOfSentenceCase(Platform.operatingSystem)}"
+              .toNativeUtf8()
+              .cast<Char>();
+      try {
+        return GomuksInit(message);
+      } finally {
+        calloc.free(message);
+      }
+    });
 
     final callable =
         NativeCallable<