Function propagate_transform 

pub fn propagate_transform(
    parent_local_to_world: &[f32; 16],
    child_local_to_parent: &[f32; 16],
) -> [f32; 16]

Propagate transforms through a parent-child hierarchy.

Given a parent’s local_to_world matrix and a child’s local_to_parent matrix, compute the child’s local_to_world.