code: function processBuffer(buffer) {
        if (!outputJSON.buffers) {
          outputJSON.buffers = [{ byteLength: 0 }];
        }
  
        // All buffers are merged before export.
        buffers.push(buffer);
  
        return 0;
      }
docs: Process a buffer to append to the default one.
  @param  {ArrayBuffer} buffer
  @return {Integer}