mathlib3

18624efa - feat(order/complete_lattice): add `Sup_diff_singleton_bot` etc (#14205)

feat(order/complete_lattice): add `Sup_diff_singleton_bot` etc (#14205) * add `Sup_diff_singleton_bot` and `Inf_diff_singleton_top`; * add `set.sUnion_diff_singleton_empty` and `set.sInter_diff_singleton_univ`.