Fix layout

[tjcrone]

Okay now that I wasted way too much time on the GitHub Action commit message, I am going to work on the config file and the layout. Below is a reminder of what the site looked like previously. If we are happy with the way it looked before, I will attempt to replicate for the most part. Thoughts? Feelings?

[rabernat]

Great, thanks!

The only thing I would change about the current layout is to try to get the logo image back.

With the new TOC structure, it's not clear to me how to make the assignments indented as they were before. But I don't think this is a big deal. We could just change the titles of all the assignments to be "Assignment: ..." and be done with it.