feat: 在表单提交按钮中添加 loading 状态

src/__fk-inputs__/inputs/form.ts

@@ -29,6 +29,7 @@ export const form: FormKitTypeDefinition = {
       props: {
         type: 'submit',
         label: '$submitLabel',
+        loading: '$state.loading || undefined',
       },
     }))(),
   ),