Basic index doesn't work for Scala 3

[yatesco]

Hi there - following https://www.scala-js.org/doc/tutorial/basic/index.html states you can use Scala 3 but then states to add scalajs-dom version of 1.1.0 which doesn't work for Scala 3.

Changing 1.1.0 to 2.0.0 allows compilation to continue.

I'm working up to my flag here so I don't know the implications of changing 1.1.0 to 2.0.0 for Scala 2, hence no PR.