Add DateTimeOffset in RegisterForAot

Author: mythz

src/ServiceStack.Text/PclExport.Net40.cs

@@ -800,9 +800,12 @@ public override void RegisterForAot()
             RegisterTypeForAot<Guid>();
             RegisterTypeForAot<TimeSpan>();
             RegisterTypeForAot<DateTime>();
-            RegisterTypeForAot<DateTime?>();
-            RegisterTypeForAot<TimeSpan?>();
+            RegisterTypeForAot<DateTimeOffset>();
+
             RegisterTypeForAot<Guid?>();
+            RegisterTypeForAot<TimeSpan?>();
+            RegisterTypeForAot<DateTime?>();
+            RegisterTypeForAot<DateTimeOffset?>();
         }
 
         [Preserve]