code: public JBBPDslBuilder BitArray(final String name, final JBBPBitNumber bits, final String sizeExpression) {
      final Item item = new Item(BinType.BIT_ARRAY, name, this.byteOrder);
      item.bitNumber = bits;
      item.sizeExpression = assertExpressionChars(sizeExpression);
      this.addItem(item);
      return this;
    }
docs: Add named bit array with size calculated through expression.
  
  @param name           name of the array, if null then anonymous one
  @param bits           length of the field, must not be null
  @param sizeExpression expression to be used to calculate array size, must not be null
  @return the builder instance, must not be null