Function robust_geo::cross_2d

pub fn cross_2d(
    a: Vector2<f64>, 
    b: Vector2<f64>, 
    c: Vector2<f64>, 
    d: Vector2<f64>
) -> f64

Computes the determinant of the following matrix

┌─                     ─┐
│ b.x - a.x   b.y - a.y │
│ d.x - c.x   d.y - c.y │
└─                     ─┘