docs: public ZipFileData addLast(ZipFileData newLastData) {
          String newLastPath = newLastData.path;
  
          Cell dupCell = cells.get(newLastPath);
          if ( dupCell != null ) {
              throw new IllegalArgumentException("Path [ " + newLastPath + " ] is already stored");
          }
  
          Cell oldLastCell = anchor.prev;
  
          Cell newLastCell = new Cell(newLastData);
          cells.put(newLastPath, newLastCell);
  
          newLastCell.putBetween(oldLastCell, anchor);
  
          return oldLastCell.data;
      }