No placeholder for Learner Profile

[ocaisa]

While preparing for a workshop on lesson design this week, I was surprised to realise that there is no placeholder in the lesson example for Learner Profiles. For SWC, for example, you can find this on the website and it is a catchall for the full workshop, but there are many people who are using the lesson example to write their own lessons and don't have such a website. Since the Learner Profile is a key part of backwards lesson design, I think it really deserves a home inside the lesson (perhaps in the _config.yml and then rendered in guide.md?)

[ocaisa]

Closing this as it is probably more an issue for the style repo: carpentries/styles#517