Wiki: Information Encoding improvements

[B-rando1]

This is just a roundup of things I noticed in the Information Encoding wiki page.

• It contains links to wiki pages ModelExpr and CodeExpr that don't exist. Since they don't exist, each one automatically re-routes to a page to create it. Is this intentional? Or should those be links to other documentation instead?
• There's a typo in The Lower Middle section: "...it is also important to not that..."
• There are TODOs and ????s. Are those sections that we are able to fill in with our current knowledge of Drasil?

Contributes to #4401

[JacquesCarette]

Looks like this was mostly me writing this, when I had a burst of time in 2021. And the burst probably intended for more to be written, and that did not happen.

It is normal for markdown pages to redirect to a create page when a link goes nowhere. This is probably fine to leave as it is.

Rather than filling-in the TODOs and ????s, probably best to look at the whole page from a high-level first, and see if it still matches our modern understanding of Drasil.