domain-modelling-tools: Use name argument in abstract class

[arkivm]

In Scala 3 Book, under Abstract classes, the example for an abstract class that can take arguments doesn't really use the argument.

abstract class Pet(name: String):
  def greeting: String
  def age: Int
  override def toString = s"I say $greeting, and I’m $age"

However, the immediate example that shows "traits with parameters" use them.

I'd be happy to send a PR.

[Philippus]

That would be great @arkivm !