mathlib3

b7f7c4aa - feat(combinatorics/simple_graph/clique): Cliques (#12982)

feat(combinatorics/simple_graph/clique): Cliques (#12982) Define cliques. Co-authored-by: Bhavik Mehta <bhavik.mehta8@gmail.com> Co-authored-by: Kyle Miller <kmill31415@gmail.com>