IO refactor/reimplementation

[andywhite37]

IO is currently a naive implementation of an effect type. It seems to work okay for simpler tasks, but lacks cancellation, and is not stack safe, and doesn't have some of the bells and whistles of the more advanced effect types, like ZIO, effect-ts, purescript Aff, xio.

This ticket is a place holder to note that we need to do something with IO. It would be great to refactor it to at least improve the stack safety situation and add cancellation, but it's not totally clear how that might affect the API. We could also consider a brand new implementation/port of another library. That would not need to live in this repository.