mathlib3

87eec0b6 - feat(linear_algebra/bilinear_form): Existence of orthogonal basis with respect to a bilinear form (#5814)

feat(linear_algebra/bilinear_form): Existence of orthogonal basis with respect to a bilinear form (#5814) We state and prove the result that there exists an orthogonal basis with respect to a symmetric nondegenerate.