Screen Safari improvements

[illicitonion]

The Screen Safari workshop in https://programming.codeyourfuture.io/structuring-data/sprints/1/day-plan/ (which is currently titled "Energiser: Popcorn" in the menu) is really useful, but currently isn't very clearly expressed for how to run it in class.

Some suggested improvements:

1. Add learning objectives around basic presentation skills
2. Make very clear that in class it should still be done on a single Google Meet call, with a volunteer plugged into a screen/projector and people dialling in. Most of the point of this workshop is to make sure everyone can share their screen on a call.
3. Add a feedback round at the end - probably not individual feedback, but a reflection discussion on "What made for an engaging vs boring story?"
4. Encourage people to prepare for this (either by better messaging "Read the Day Plan before coming to class", or by adding a backlog item to explicitly instruct it, or maybe both!)

[illicitonion]

This was done in #1832 and #1833 and #1834