chore: always allow discord for mac and windows (#958)

lib/app_config.dart

@@ -1,6 +1,10 @@
-// TODO(#946): make discord work inside the snap
-// or leave it for linux disabled if this won't work
+import 'dart:io';
+
 import 'package:flutter/foundation.dart';
 
+// TODO(#946): make discord work inside the snap
+// or leave it for linux disabled if this won't work
 bool allowDiscordRPC = kDebugMode ||
+    Platform.isMacOS ||
+    Platform.isWindows ||
     bool.tryParse(const String.fromEnvironment('ALLOW_DISCORD_RPC')) == true;