message: gltfpack: Use ktx2 extension for KTX2 files
  This is more correct than ktx that usually refers to KTX1.
diff: @@ -2943,7 +2943,7 @@ void writeImage(std::string& json, std::vector<BufferView>& views, const cgltf_i
  if (settings.texture_basis)
  {
  std::string full_path = getFullPath(image.uri, input_path);
  - std::string basis_path = getFileName(image.uri) + (settings.texture_ktx2 ? ".ktx" : ".basis");
  + std::string basis_path = getFileName(image.uri) + (settings.texture_ktx2 ? ".ktx2" : ".basis");
  std::string basis_full_path = getFullPath(basis_path.c_str(), output_path);
  if (readFile(full_path.c_str(), img_data))
  