mathlib3

89a3c072 - feat(field_theory/laurent): Laurent expansions of rational functions (#11199)

feat(field_theory/laurent): Laurent expansions of rational functions (#11199) Also provide more API for `ratfunc`, lifting homomorphisms of (polynomial to polynomial) to (ratfunc to ratfunc). Co-authored-by: Yakov Pechersky <pechersky@users.noreply.github.com> Co-authored-by: Yakov Pechersky <ypechersky@treeline.bio>