helper to convert option to result with transform

[joprice]

I may have overlooked a helper in either this or the standard library, but I end up finding this function useful, similar to requireSome but where the fallback is evaluated on demand.

let fromOption f = (unit -> 'a) -> option<'b> -> Result<'b,'a> 
      function
      | Some value -> Ok value
      | None -> Error(f ())

Is there an equivalent or would it make sense to add perhaps Result.requireSomeWith?

[TheAngryByrd]

Agreed! Seem like a good PR to have:

• Add requireSomeWith and requireNoneWith
• Add to Result, AsyncResult, TaskResult, JobResult
• Add corresponding tests