Initial stab at a pose visualisation

[DRMacIver]

This adds a visualisation for helping people get an intuition for how a pose relates to a hidden pose. Hopefully it's more or less what you had in mind!

Things currently lacking from it:

• The pose is fixed and adjustable rather than random. I'm not actually sure this is bad, but it would be easy to add a random button (the hard part is making sure the random location is sensible)
• The update is really slow. There are probably some things I can do to improve that but initial experiments weren't super promising.
• I'm not super happy with how it displays the score.

Also I've not written any prose or anything around it, just implemented a basic visualisation.