fix(review report): return readable image list in csv

array.join docs

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/join

that check is only there to prevent the separator from being at the beginning of the string. you don't need it if you concatenate the image sources using array.join.

if you're asking how array.join does this in code, it's native code, i haven't seen what it explicitly does.