mathlib

0f9edf98 - feat(data/set/[basic|prod]): make `×ˢ` bind more strongly, and define `mem.out` (#13422)

feat(data/set/[basic|prod]): make `×ˢ` bind more strongly, and define `mem.out` (#13422) * This means that `×ˢ` does not behave the same as `∪` or `∩` around `⁻¹'` or `''`, but I think that is fine. * From the sphere eversion project