Add progress cards to the deck

[tmtmtmtm]

After every 15-20th person*, add a non-person card to the deck congratulating/encouraging the user, and reinforcing the value of what they're doing.

This should help break the fatigue a little, introduce a little more novelty and fun, and subtly reinforce that the answers actually matter: it's not just a game, people will actually be using the data generated from this, etc.

These could be generated from suitable list of headlines, messages, and images and then shuffled throughout the deck.

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• exact number to be determined, though perhaps we should make it semi-random within that sort of range, rather than a fixed number.

[MyfanwyNixon]

Some rah rah phrases are here: https://docs.google.com/document/d/1t1oV2ophAIIhun4Dd4Q19LpuQCNFTTyVk6BXF4nPZ3g/edit

I'm keen to see them in situ so I can gauge whether they actually work.

[andylolz]

Ahh, this is a nice easy way of achieving something similar to #160.