function addFixtureFiles(spriter, files) {
  for (const file of files) {
    const filePath = path.join(cwd, file);
    spriter.add(path.resolve(filePath), file, fs.readFileSync(filePath, 'utf8'));
  }

  return spriter;
}
Add a bunch of SVG files

@param {SVGSpriter} spriter          Spriter instance
@param {Array} files                 SVG files
@returns {SVGSpriter}                Spriter instance