修复表单组件样式和单元测试用例 (#7)

* fix: loading small style, search style and dialog style

* fix: scroll to top

* fix mobile scroll

* fix scroll to top

* 文档细节优化

* unit test

* dialog and image-preview unit test

* fix form component style

* fix radio and checkbox style

* fix search component style

packages/dialog/src/dialog.vue

@@ -60,12 +60,14 @@ export default {
     },
 
     close() {
+      /* istanbul ignore if */
       if (this.closing) return;
 
       this.closing = true;
 
       this.value = false;
 
+      /* istanbul ignore else */
       if (this.lockOnScroll) {
         setTimeout(() => {
           if (this.overlay && this.bodyOverflow !== 'hidden') {