code: function Preprocessor(config, logger) {
    const log = logger.create('preprocessor.gzip');
  
    return (content, file, done) => {
      const originalSize = content.length;
      // const contentBuffer = Buffer.isBuffer(content) ? content : Buffer.from(content);
  
      zlib.gzip(content, (err, gzippedContent) => {
        if (err) {
          log.error(err);
          done(err);
          return;
        }
  
        // eslint-disable-next-line no-param-reassign
        file.encodings.gzip = gzippedContent;
  
        log.info(`compressed ${file.originalPath} [${util.bytesToSize(originalSize)} -> ${util.bytesToSize(gzippedContent.length)}]`);
        done(null, content);
      });
    };
  }
docs: Preprocess files to provide a gzip compressed alternative version