type class derivation with scala 3 instead of shapeless

[gregor-i]

Hi @theon,

I've continued your branch towards scala 3. Please note that the PR target is the branch scala3 instead of master.

I've removed the shapeless dependency by migrating to scala 3 type class derivation. The tests are green on my local maschine.

I had to disable scalafmt, as it could not parse the type class derivation code.

[theon]

Thanks for this! I've have released this as version 4.0.0-M1 for Scala 3, but I'm holding off merging to master as ideally I'd like a solution that will cross compile for Scala 3 and 2.13.

If shapeless 2 doesn't make it to Scala 3 soon, I'll investigating duplicating PathPart.scala and QueryKeyValue.scala into scala version specific source directories; a src/main/scala-3/ with this implementation and a src/main/scala-2.13/ with the shapeless implementation

Note: 4.0.0-M1 is not yet published for Scala.js; I think this needs some more attention to get the tests passing.

Thanks again for the contribution!