Feature Proposal: Add unwrapOrElse method to Result

Introduce a new instance method on Result and ResultAsync

```
unwrapOrElse<U>(op: (err: E) => U): T | U
```
- Success (Ok): returns the contained T.
- Failure (Err): calls the provided callback op with the error E and returns the callback’s return value.

This would prevent having to use `.match` with a callback such as `(value) => value`, in the first parameter.