added select overload with projection for result

[christophercalm]

This extension allows you to use the linq query syntax for result as we are currently already able to do using maybe.

Whereas this code worked before

Maybe<string> name = "John";

var upper = from x in name select x.ToUpper();

This very similar code would not

Result<string> name = "John";

var upper = from x in name select x.ToUpper();

Adding an overload to Select with a projection allow for greater flexibility in monadic operations using the linq query syntax which enables the user to pass in values from previous operations down the monadic chain.

This is related to issue 566

[vkhorikov]

Answered here: #566 (comment)