spec: Add connectivity_method == 0 to Sequential decoder
spec: Add connectivity_method == 0 to Sequential decoder

This addresses a comment in KhronosGroup/glTF#1114

louquillio/draco,louquillio/draco,google/draco,google/draco,louquillio/draco,google/draco,louquillio/draco,google/draco,louquillio/draco,google/draco,google/draco,google/draco,louquillio/draco