mathlib3

b3915636 - feat(algebra/lie_algebra): conjugation transformation for Lie algebras of skew-adjoint endomorphims, matrices (#3229)

feat(algebra/lie_algebra): conjugation transformation for Lie algebras of skew-adjoint endomorphims, matrices (#3229) The two main results are the lemmas: * skew_adjoint_lie_subalgebra_equiv * skew_adjoint_matrices_lie_subalgebra_equiv The latter is expected to be useful when defining the classical Lie algebras of type B and D.