mathlib

4e50b688 - feat(category_theory/abelian): if D is abelian so is C ⥤ D (#13686)

feat(category_theory/abelian): if D is abelian so is C ⥤ D (#13686) Needed for LTE, and also useful to show `Rep k G` is abelian. Co-authored-by: Scott Morrison <scott.morrison@gmail.com>