message: gltfpack: Avoid parsing mesh.extras twice
  Instead, manually copy token start/end before parsing extras.
diff: @@ -2012,16 +2012,15 @@ static int cgltf_parse_json_mesh(cgltf_options* options, jsmntok_t const* tokens
  }
  else if (cgltf_json_strcmp(tokens + i, json_chunk, "extras") == 0)
  {
  - int skip = cgltf_parse_json_extras(tokens, i + 1, json_chunk, &out_mesh->extras);
  - if (skip < 0)
  - {
  - return skip;
  - }
  + ++i;
  - if (tokens[i+1].type == JSMN_OBJECT)
  + out_mesh->extras.start_offset = tokens[i].start;
  + out_mesh->extras.end_offset = tokens[i].end;
  +
  + if (tokens[i].type == JSMN_OBJECT)
  {
  - int extras_size = tokens[i+1].size;
  - i += 2;
  + int extras_size = tokens[i].size;
  + ++i;
  for (int k = 0; k < extras_size; ++k)
  {
  @@ -2042,8 +2041,10 @@ static int cgltf_parse_json_mesh(cgltf_options* options, jsmntok_t const* tokens
  }
  }
  }
  -
  - i = skip;
  + else
  + {
  + i = cgltf_skip_json(tokens, i);
  + }
  }
  else
  {
  