Moving the syllabus to public visibility?

My feeling is that we are within a week or two of being able to open the learning track to wider visibility, at least in preliminary form (but no promises!). Then we can get feedback on what works and what needs fixing.

I don't want to get into a full critical path analysis (Microsoft Project! GANTT charts! I did more than enough of this when I worked in industry!!). More roughly, these are the key steps I can think of:

- Implement the concepts that others have as a prereq. As far as I can see, this means `functions` (`locomotive-engineer`, in progress) and `tuples` (`tisbury-treasure-hunt` or something equivalent). Others are nice to have, but I think they can be added later.
- Check all the prereqs are correct, once all the relevant concepts are in place. For example, `high-school-sweetheart` will need to change, perhaps to ["functions", "strings"].
- Add "practices" entries for some more Practice Exercises. I did a couple of these a few days ago, just to test the process. For inspiration, I made a [sheet](https://docs.google.com/spreadsheets/d/1OprA7-ch1_Jub2Zze62otK1-xemjx2D3FUTEFkVsJFM/edit?usp=sharing) with tabs for various other tracks, showing what they chose. Of course, idioms differ, so these may not translate directly to Julia.

For visibility, we need `"concept_exercises": true` near the top of the `config.json`, as Glenn pointed out on the forum. I think we also need to change to `"status": "beta"` for each exercise, but that needs to be confirmed.

Anything else?