changing u1-d01-welcome slides to Quarto

[tracykteal]

Updated the slides in u1-d01-welcome to Quarto according to the guidance in #154

Also updated some things in setup.md that will apply for all the slide conversions.

I compared these with the originals and they all looked very close to the same. Still could use a check to make sure.

[tracykteal]

The URL being linked doesn't come through in 'author' with Quarto. Should we just take that out?

So author: "datasciencebox.org" instead of author: "[datasciencebox.org](https://datasciencebox.org/)"

[tracykteal]

@mine-cetinkaya-rundel if this approach looks good, I can work on other slides, and have someone who might be able to do some as well.