Build generic derivation of UIs

[noelwelsh]

Build generic derivation / type directed metaprogramming construction of UIs. So give, for example, a case class we can automatically construct a UI that renders it, and a form that fills it in.

It would be useful to have this for functions as well, to support Doodle Explore.

Look at Scala 3 libraries for this: Magnolia and Shapeless.