(minor) Introduction episode has an exercise which isn't counted in time

[glenn-horton-smith]

_episodes/01-introduction.md has an exercise -- compiling "hello world" -- but the header at the top says 0 minutes for exercises, and the exercise isn't formatted like the exercises in the python carpentry module.
(I'd like to make a PR for this minor issue just to learn a little more about the carpentry setup and exercise the workflow.)

[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. Please manually close it, if it is no longer relevant, or ask for help or support to help getting it unstuck. Let me bring this to the attention of @klieret @wdconinc @michmx for now.