Support for Scala 3

[nvollmar]

Are there plans to update this library to Scala 3?

[viswanath7]

It'd be very much appreciated if Scala 3 can be supported.

[MartinHH]

As shapeless 3 for scala 3 is a totally different library from shapeless 2, migrating this to scala 3 would more or less require a full rewrite.

Note that there are alternatives for scala 3:

1. https://github.com/MartinHH/scalacheck-derived implements derivation for all scalacheck typeclasses using plain scala 3 typeclass derivation
2. https://github.com/softwaremill/magnolia should make it rather simple to implement your own derivation of Arbitrary etc