mathlib

98a20c25 - feat(combinatorics/simple_graph/matching): introduce matchings and perfect matchings of graphs (#5156)

feat(combinatorics/simple_graph/matching): introduce matchings and perfect matchings of graphs (#5156) Introduce definitions of matchings and perfect matchings of graphs. This is with the goal of eventually proving Hall's Marriage Theorem and Tutte's Theorem. Co-authored-by: agusakov <39916842+agusakov@users.noreply.github.com>