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/image-preview/src/image-preview.vue

@@ -74,9 +74,10 @@ export default {
 
       this.value = false;
 
+      /* istanbul ignore else */
       if (this.lockOnScroll) {
         setTimeout(() => {
-          if (this.modal && this.bodyOverflow !== 'hidden') {
+          if (this.overlay && this.bodyOverflow !== 'hidden') {
             document.body.style.overflow = this.bodyOverflow;
           }
           this.bodyOverflow = null;