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

docs/examples-docs/button.md

@@ -7,9 +7,14 @@
     }
     .van-row {
       padding: 0 15px;
+      margin-bottom: 20px;
     }
-    .van-col {
-      margin-bottom: 10px;
+    .van-col-24 {
+      margin-bottom: 20px;
+
+      &:last-child {
+        margin-bottom: 0;
+      }
     }
   }
 }
@@ -93,18 +98,12 @@ export default {
   <van-col span="24">
     <van-button size="large">large</van-button>
   </van-col>
-</van-row>
-<van-row>
   <van-col span="24">
     <van-button size="normal">normal</van-button>
   </van-col>
-</van-row>
-<van-row>
   <van-col span="24">
     <van-button size="small">small</van-button>
   </van-col>
-</van-row>
-<van-row>
   <van-col span="24">
     <van-button size="mini">mini</van-button>
   </van-col>