message: Fix JavaScript source maps
  Closes
diff: @@ -29,13 +29,12 @@ export default function (userOptions = {}) {
  if (options.sourceMap) {
  terserOptions.sourceMap = {
  filename,
  - // Filename is path, so just need basename
  url: basename(filename) + ".map",
  };
  }
  try {
  - const output = await minify(content, terserOptions);
  + const output = await minify({ [filename]: content }, terserOptions);
  file.content = output.code;
  if (output.map) {
  