message: [node] Remove `.toString()` in nft `readFile()` hook
  The nft `readFile()` hook accepts `Buffer` type so there's no reason to `.toString()` here.
diff: @@ -195,10 +195,11 @@ async function compile(
  ignore: config.excludeFiles,
  async readFile(fsPath: string): Promise<Buffer | string | null> {
  const relPath = relative(baseDir, fsPath);
  +
  + // If this file has already been read then return from the cache
  const cached = sourceCache.get(relPath);
  - if (cached) return cached.toString();
  - // null represents a not found
  - if (cached === null) return null;
  + if (typeof cached !== 'undefined') return cached;
  +
  try {
  let source: string | Buffer = readFileSync(fsPath);
  if (
  @@ -216,9 +217,10 @@ async function compile(
  }
  fsCache.set(relPath, entry);
  sourceCache.set(relPath, source);
  - return source.toString();
  + return source;
  } catch (e) {
  if (e.code === 'ENOENT' || e.code === 'EISDIR') {
  + // `null` represents a not found
  sourceCache.set(relPath, null);
  return null;
  }
  