code: public GridBagLayoutBuilder append(Component component, int colSpan, int rowSpan) {
          return append(component, colSpan, rowSpan, 0.0, 0.0);
      }
docs: Appends the given component to the end of the current line, using the
  default insets and no expansion
  
  @param component the component to add to the current line
  @param colSpan   the number of columns to span
  @param rowSpan   the number of rows to span
  
  @return "this" to make it easier to string together append calls