write-imports.js

function copyData(srcFile, cssImport) {
  let cssImports;
  
  fs.readFile(srcFile, 'utf8', function (err, data) {
      if (err) throw err;
      
      cssImports = `
          ${data}; \n
          @import ${csssImport};
      `;
    
      //Do your processing, MD5, send a satellite to the moon, etc.
      fs.writeFile (srcFile, cssImports, function(err) {
          if (err) throw err;
          console.log('complete');
      });
  });
}