Feature: add support for Infinity and NaN

[BBI-YggyKing]

Allow float and double special cases to be converted to and from json correctly, including positive and negative infinity and NaN.

[Ragzouken]

Not sure if I should post this as a separate issue or not, but in the mean time when this enhancement is not being worked on, it feels like a bug that a NaN will silently serialized to invalid JSON that can't be deserialized again.