Added support for date and date-time

[gius]

I have added a simple date and date-time support. Unfortunately, I was not able to figure out how to properly add a shared type

export const ParsedDate = z.preprocess(arg => (typeof arg == "string" || arg instanceof Date ? new Date(arg) : undefined), z.date());

So I have inlined the logic. (based on https://github.com/colinhacks/zod#dates)

Could you please have a look?
Because of that, I have not updated test snapshots. :-(

[josejulio]

Hello- I'll take a look - I suppose we should have a function to do this that deals with the adding the type if not found and just returning it.

[josejulio]

I guess this is good for now. Created #7 to add a way to add shared types.