Add initial structure of a Magic School Bus puzzle

This has the same sort of introduction as the TARDIS puzzle (zooming
into the time machine), but this time it's the Magic School Bus, not
the TARDIS, of course.

Then, there's an interactive form for making some turtle art, and an
image showing the result. Currently, the result is hard-coded inside
the script, but it should be simple to make it consume the form input,
(which is already being sent to the server at least).