fix: extra foot miss style (#738)

Author: zombieJ

src/PickerInput/Popup/Footer.tsx

@@ -107,7 +107,7 @@ export default function Footer(props: FooterProps) {
 
   return (
     <div className={`${prefixCls}-footer`}>
-      {extraNode}
+      {extraNode && <div className={`${prefixCls}-footer-extra`}>{extraNode}</div>}
       {rangeNode}
     </div>
   );

src/utils/getExtraFooter.tsx

@@ -498,7 +498,7 @@ describe('Picker.Basic', () => {
     );
 
     function matchFooter(mode: string) {
-      expect(document.querySelector('.rc-picker-footer').textContent).toEqual(mode);
+      expect(document.querySelector('.rc-picker-footer-extra').textContent).toEqual(mode);
       expect(renderExtraFooter.mock.calls[renderExtraFooter.mock.calls.length - 1][0]).toEqual(
         mode,
       );

tests/picker.spec.tsx

@@ -144,7 +144,7 @@ describe('Picker.Range', () => {
         <DayRangePicker renderExtraFooter={() => <p>footer</p>} picker="year" />,
       );
       openPicker(container);
-      expect(document.querySelector('.rc-picker-footer').textContent).toEqual('footer');
+      expect(document.querySelector('.rc-picker-footer-extra').textContent).toEqual('footer');
       expect(document.querySelectorAll('.rc-picker-header-view')[0].textContent).toEqual(
         '1990年-1999年',
       );