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
Whew! Seems like a pretty clean one? Ran `rails app:upgrade` and stuff, and made some corrections to keyword arguments for `translate` calls. There might be more such problems elsewhere? But that's hard to search for, and we'll have to see.
