feat(library/data/fin): add foldl and foldr
feat(library/data/fin): add foldl and foldr

fgdorais/lean,soonhokong/lean-osx,dselsam/lean,leanprover-community/lean,UlrikBuchholtz/lean,c-cube/lean,leanprover-community/lean,levnach/lean,rlewis1988/lean,leodemoura/lean,soonhokong/lean-windows,avigad/lean,digama0/lean,c-cube/lean,avigad/lean,javra/lean,johoelzl/lean,sp3ctum/lean,Kha/lean,UlrikBuchholtz/lean,johoelzl/lean,soonhokong/lean-windows,fpvandoorn/lean,eigengrau/lean,fpvandoorn/lean,UlrikBuchholtz/lean,fpvandoorn/lean2,fgdorais/lean,soonhokong/lean-windows,johoelzl/lean,leodemoura/lean,eigengrau/lean,avigad/lean,eigengrau/lean,leodemoura/lean,fgdorais/lean,fpvandoorn/lean2,johoelzl/lean,leanprover-community/lean,sp3ctum/lean,fpvandoorn/lean,eigengrau/lean,UlrikBuchholtz/lean,rlewis1988/lean,soonhokong/lean-windows,soonhokong/lean-osx,levnach/lean,soonhokong/lean-windows,avigad/lean,rlewis1988/lean,soonhokong/lean-osx,digama0/lean,c-cube/lean,sp3ctum/lean,leanprover-community/lean,digama0/lean,Kha/lean,soonhokong/lean-osx,sp3ctum/lean,digama0/lean,sp3ctum/lean,fpvandoorn/lean,leanprover/lean,fgdorais/lean,fgdorais/lean,rlewis1988/lean,rlewis1988/lean,levnach/lean,soonhokong/lean,johoelzl/lean,c-cube/lean,fpvandoorn/lean2,javra/lean,leanprover/lean,johoelzl/lean,leanprover/lean,UlrikBuchholtz/lean,soonhokong/lean,avigad/lean,leodemoura/lean,soonhokong/lean,soonhokong/lean,leodemoura/lean,levnach/lean,eigengrau/lean,levnach/lean,javra/lean,leanprover-community/lean,soonhokong/lean,fpvandoorn/lean,Kha/lean,leanprover/lean,digama0/lean,fpvandoorn/lean,dselsam/lean,rlewis1988/lean,dselsam/lean,leodemoura/lean,digama0/lean,fpvandoorn/lean2,avigad/lean,javra/lean,c-cube/lean,dselsam/lean,soonhokong/lean-osx,leanprover-community/lean,javra/lean,leanprover/lean,Kha/lean,dselsam/lean,leanprover/lean,Kha/lean,dselsam/lean,fpvandoorn/lean2,fgdorais/lean,Kha/lean