Function compute_default_blues 

fn compute_default_blues(
    shaper: &Shaper<'_>,
    coords: &[F2Dot14],
    style: &StyleClass,
) -> SmallVec<UnscaledBlue, MAX_BLUES>

Compute unscaled blue values for the default script set.

See https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/autofit/aflatin.c#L314