Add info to the curriculum

Or could put info in another doc, or just have it as an option in the app, eg `kosu info geocomp-ml`

E.g.

- Number of code cells
- Number of exercise
- Imports / dependencies
- Datasets used
- Images used, not that relevant

Some of those are more relevant to the curriculum than others.

This would be easier if we do the notebook dict thing mentioned in #1 