Add Mill support to Tutorials

[nderraugh]

This refers to #579

The context for the task is not well defined. So I started with just the first tutorial. I thought I should push something small to start to see how it might fit in.

Essentially I reproduced the first tutorial but adapted it to use the Mill build tool.

If this is still something you are interested in, would you be able to provide any guidance about how you would like to see it structured in the documentation?

If you would like I can continue to integrate this into the documentation and code sample repository. I have worked through this for all three stages of the Getting Started with Scala.js and Vite using Mill. You can find the code here: https://github.com/nderraugh/scalajs-mill-vite-laminar-chartjs-example with some tags for the three different tutorials.

For this PR I created three commits to help with review. Specifically to try to help with the diff between the sbt version and the mill version.