Scala 3 introduced scala.util.NotGiven: a special class used to implement negation in implicit search.
While techniques existed to implement this functionality in Scala 2, the NotGiven trait was not
backported to Scala 2. This makes cross-compilation more frustrating than it needs to be, so this
library was created to make a single com.dwolla.compat.scala.util.NotGiven available to
Scala 2.12, 2.13, and 3.