epic: html is not escaped

[machow]

#14 mentions the intended behavior in Great Tables is to escape html, unless someone uses html(). However, as our sports earning example shows, HTML in the cell body is not escaped.

This is mentioned here: https://github.com/posit-dev/great-tables/issues/134#issuecomment-1977498070

We need to decide what to do, and resolve this. It's likely people are already using this behavior, so we should be careful to take that into account.