Add value property to Result

[Nevin]

I cite previous forum threads about typed throws:

@dabrahams

And experience in still others, like C++ and Java, suggests that
using static types to restrict the kind of information a function can
give you when an error occurs may actually be harmful.

@John_McCall

For those programmers, typed throws is just going to box them in and force them into anti-patterns in the long run.

(The entirety of that comment by John McCall is worth reading.)