add target_error for gltfpack simplification

[arpu]

gltf-transform https://github.com/donmccurdy/glTF-Transform/blob/ef4e81ac80baaf4f1d95aeb8bd9d5c9c08584cba/packages/functions/src/simplify.ts#L49C4-L49C91

allows to set the target error on simplification

• ratio=0.0, error=0.0001: Aims for maximum simplification, constrained to 0.01% error.

would be nice to have this for gltfpack

[zeux]

Yeah this is tracked in #494, it's complicated by the fact that gltfpack currently dynamically selects the error based on the algorithm chosen, but maybe that's fine if we just ignore the error when using aggressive simplification or maybe this can be specified in some other way.

[arpu]

at this note would be nice to have the meshopt_simplifyWithAttributes mode too
3 different simplify modes with optional error target

[zeux]

Yeah that’s tracked in #652