code: public GridBagLayoutBuilder appendField(Component component, int colSpan) {
          return append(component, colSpan, 1, true, false);
      }
docs: Appends the given component to the end of the current line. The component
  will "grow" horizontally as space allows.
  
  @param component the item to append
  @param colSpan   the number of columns to span
  
  @return "this" to make it easier to string together append calls