code block for README-17

README-17

// Shuffle inner letter array
for (var i = start; i < end; i++) {
  // Choose a random index in region
  final var rndIdx =
    start + random.nextInt(length);
  // Swap current/random chars
  final var save = result[rndIdx];
  result[rndIdx] = result[i];
  result[i] = save;
}