Consider supporting Scala 2.13

[altrack]

Hey SoftwareMill,

Since the introduction of project Loom there is a lot of interest in going back to direct style code from monads. Yet, most of the industry is still using Scala 2. Structured concurrency and scoped values will be probably GA in one of the next JVM versions, much sooner than the industry will move to Scala 3 (if at all). Please consider adding Scala 2.13 support.

Thanks.