mathlib

ade30c34 - feat(data/int/basic): Lemmas for when a square equals 1 (#14501)

feat(data/int/basic): Lemmas for when a square equals 1 (#14501) This PR adds two lemmas for when a square equals one. The `lt` lemma will be useful for irreducibility of x^n-x-1. Co-authored-by: tb65536 <tb65536@users.noreply.github.com>