fix: use type discriminating deserialiser

Plugin.cs

@@ -27,7 +27,14 @@ public class Plugin : IDalamudPlugin {
 
     internal static IDeserializer Deserializer { get; } = new DeserializerBuilder()
         .WithNamingConvention(UnderscoredNamingConvention.Instance)
-        .WithTypeConverter(new WhenConverter())
+        // .WithTypeConverter(new WhenConverter())
+        .WithTypeDiscriminatingNodeDeserializer(o => {
+            var keyMappings = new Dictionary<string, Type> {
+                ["quest"] = typeof(WhenQuest),
+            };
+
+            o.AddUniqueKeyTypeDiscriminator<IWhen>(keyMappings);
+        })
         .Build();
 
     private static class Signatures {