Shader Instancing example does not render additional instanced entites with respect to their Transforms about bevy

[DavidHospital]

Upon further investigation, I believe this is explained by the following comment in https://github.com/bevyengine/bevy/blob/release-0.13.2/assets/shaders/instancing.wgsl#L21-L24:

// NOTE: Passing 0 as the instance_index to get_model_matrix() is a hack
// for this example as the instance_index builtin would map to the wrong
// index in the Mesh array. This index could be passed in via another
// uniform instead but it's unnecessary for the example.
I think it would be helpful to include some example somewhere demonstrating how to get the index described in this comment, as to me it is unclear.