list 的 placeholder 支持 html或者其他渲染器

scss/components/_list.scss

@@ -78,7 +78,7 @@
   &-placeholder {
     color: $text--muted-color;
     text-align: center;
-    height: $List-placeholder-height;
+    min-height: $List-placeholder-height;
     line-height: $List-placeholder-height;
   }
 }

src/renderers/List.tsx

@@ -789,7 +789,9 @@ export default class List extends React.Component<ListProps, object> {
             )}
           </div>
         ) : (
-          <div className={cx('List-placeholder')}>{__(placeholder)}</div>
+          <div className={cx('List-placeholder')}>
+            {render('placeholder', __(placeholder))}
+          </div>
         )}
 
         {this.renderFooter()}