If possible, highlight changes to be made to files

[jhodgdon-drp]

Issue description

On pages such as django_models, participants are asked to create files, and later modify them.

A suggestion was made that it would be really helpful if in the code section that shows what to type, it was able to highlight the changes.

I am not sure if this is feasible in Markdown, but I think it would be helpful.... is this possible?

[jhodgdon-drp]

I looked through the Markdown specs and I didn't find anything obvious that would make this happen within a code block. I guess we could use some custom HTML instead of a code block, but that would make the tutorial pretty hard to maintain. So, this idea is most likely a Won't Fix. Too bad! I'll leave it open for comment though...