Include caveat in the docs about Option<Option<'t>> roundtrip

[Zaid-Ajaj]

Because Fable erasing Some None into null can cause problems when deserializing back to Some None. This is a weird edge case because null here can mean both None or Some None

[0x53A]

I think Fable does some extra work to track Some None:

In the Fable Repl

let someNone = Some None
console.log(someNone)

[Zaid-Ajaj]

Hi @0x53A, thanks for checking this out! if the structure of a nested optional is maintained when transferred, then we should be able to support the conversion properly. Then I will add a couple of tests to see how it goes