Adding an alternative version of the method whenA with a different signature

[a-khakimov]

Currently, the cats has a syntax whenA with the signature:

def whenA(cond: Boolean)(implicit F: Applicative[F]): F[Unit]

However, it would be beneficial to add an alternative version of this syntax to allow returning a result of type F[A] if the condition is true, and otherwise returning a default value.

Proposed Signature:

def whenA[A](cond: Boolean)(default: F[A])(implicit F: Applicative[F]): F[A]

It is possible with a different name.

This syntax will provide more flexibility in using conditional expressions