function firaFont(width, weight) {
  const pathInProject = 
  `fonts/Fira/FiraSans${width === 'Normal' ? '' : width}-${weight}.json`;
  const fullPath = expandPath(pathInProject);
  if (!fs.existsSync(fullPath))
    throw Error(`Dumped Fira ${pathInProject} is not found.`);
  return readJSON(pathInProject);
}
Get the Fira Sans font data
@param { 'Normal' | 'Compressed' | 'Condensed' } width Specified width
@param { 'Two' | 'Four' | 'Eight' | 'Hair' | 'Thin' | 'UltraLight' 
| 'ExtraLight' | 'Light' | 'Book' | 'Regular' | 'Medium' | 'SemiBold' 
| 'Bold' | 'ExtraBold' | 'Heavy' } weight Specified weight