code: public GridBagLayoutBuilder appendLabel(JLabel label, int colSpan) {
          return append(label, colSpan, 1, false, false);
      }
docs: Appends the given label to the end of the current line. The label does
  not "grow."
  
  @param label   the label to append
  @param colSpan the number of columns to span
  
  @return "this" to make it easier to string together append calls