Function lyon_geom::cubic_to_quadratic::single_curve_approximation

pub fn single_curve_approximation<S: Scalar>(
    cubic: &CubicBezierSegment<S>
) -> QuadraticBezierSegment<S>

This is terrible as a general approximation but works well if the cubic curve does not have inflection points and is "flat" enough. Typically usable after subdiving the curve a few times.