message: feat(Form): support using stepper
diff: import { createNamespace, isDef, addUnit } from '../utils';
  import { resetScroll } from '../utils/dom/reset-scroll';
  import { preventDefault } from '../utils/dom/event';
  +import { FieldMixin } from '../mixins/field';
  const [createComponent, bem] = createNamespace('stepper');
  @@ -18,6 +19,8 @@ function add(num1, num2) {
  }
  export default createComponent({
  + mixins: [FieldMixin],
  +
  props: {
  value: null,
  integer: Boolean,
  