The silly motivation is that I wanted to remove `.prettierignore`,
which just exists to omit that one folder from `npm run format`. But it
also seems like this is the standard place to put them—a standard
created long after we first set this up lol
The most notable thing here is that we keep the movie iframes running!
So if you're trying different pets for an animated item, the animation
keeps going while the new pet layers load alongside it.
This is also nice for like, the species/color picker form, so we're not
taking away input elements from people who depend on e.g. keyboard
focus.
