Missing doc for JsonSerializer.DeserializeAsync returns

Hi,
In the generic methods, the return type is nullable, but there is no documentation on how it is possible. Is it possible?

Also, it is minor, but the sections `Exceptions` aren't formatted the same way in the 5 methods: exceptions aren't in the same order and the JsonException have 2 different look.

Article: https://learn.microsoft.com/dotnet/api/system.text.json.jsonserializer.deserializeasync?view=net-8.0