question blocks missing in episode source files

[tobyhodges]

As reported by @jwagan in carpentries/carpentries.org#1639, learning objectives are not displayed on the episode pages of this lesson.

This is a result of the transition to the new lesson infrastructure, which requires a questions block in addition to the objectives block present in the source .Rmd files. Most lessons had questions for each episode already, but this one did not. To fix it, these questions blocks need to be added to each episode.