文档细节优化，search、咯阿丁和dialog组件样式修复 (#5)

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

* fix: scroll to top

* fix mobile scroll

* fix scroll to top

packages/loading/src/loading.vue

@@ -1,5 +1,5 @@
 <template>
-  <div class="van-loading">
+  <div class="van-loading" :class="['van-loading--' + type]">
     <span class="van-loading__spinner" :class="['van-loading__spinner--' + type, 'van-loading__spinner--' + color]"></span>
   </div>
 </template>