mathlib

b9ccb8fa - feat(algebraic_topology/simplicial_objects + ...): Truncated simplicial objects + skeleton (#6711)

feat(algebraic_topology/simplicial_objects + ...): Truncated simplicial objects + skeleton (#6711) This PR adds truncated simplicial objects and the skeleton functor (aka the truncation functor). Co-authored-by: Scott Morrison <scott.morrison@gmail.com>