feat(NumberKeyboard): add collapse icon (#6152)

src/number-keyboard/Key.js

@@ -1,6 +1,7 @@
 import { createNamespace } from '../utils';
 import { TouchMixin } from '../mixins/touch';
 import DeleteIcon from './DeleteIcon';
+import CollapseIcon from './CollapseIcon';
 
 const [createComponent, bem] = createNamespace('key');
 
@@ -50,6 +51,7 @@ export default createComponent({
     },
 
     genContent() {
+      const isExtra = this.type === 'extra';
       const isDelete = this.type === 'delete';
       const text = this.slots('default') || this.text;
 
@@ -57,6 +59,10 @@ export default createComponent({
         return text || <DeleteIcon class={bem('delete-icon')} />;
       }
 
+      if (isExtra) {
+        return text || <CollapseIcon class={bem('collapse-icon')} />;
+      }
+
       return text;
     },
   },