Add optional field support to Comparison table

[RobertVillalba]

Sorry wasn't sure where to put this suggestion, but I think one of the best things that this library has over RHF is that it seems to support setting optional fields to undefined. RHF doesn't seem to currently support setting undefined values anywhere and they don't plan to support it. This omission is a huge hindrance, specially when working with TS, since you might have to drastically change nested types, schemas, and then cast data to and from form variants. I didn't see this benefit listed in the table at https://tanstack.com/form/latest/docs/comparison and I think it would be a huge selling point.