addFirst method
- E element
override
    Adds value at the beginning of the queue.
Implementation
@override
void addFirst(E element) {
  _head = (_head - 1) & (_table.length - 1);
  _table[_head] = element;
  if (_head == _tail) _grow();
}Adds value at the beginning of the queue.
@override
void addFirst(E element) {
  _head = (_head - 1) & (_table.length - 1);
  _table[_head] = element;
  if (_head == _tail) _grow();
}