[new feature] Button: add loading-size prop (#1346)

packages/button/README.md

@@ -76,6 +76,7 @@
 | disabled | 是否禁用按钮 | `Boolean` | `false` |
 | loading | 是否显示为加载状态 | `Boolean` | `false` |
 | loading-text | 加载状态提示文字 | `String` | - |
+| loading-size | 加载图标大小 | `String` | `20px` |
 | open-type | 微信开放能力，具体支持可参考 [微信官方文档](https://mp.weixin.qq.com/debug/wxadoc/dev/component/button.html) | `String` | - |
 | app-parameter | 打开 APP 时，向 APP 传递的参数 | `String` | - |
 | lang | 指定返回用户信息的语言，zh_CN 简体中文，<br>zh_TW 繁体中文，en 英文 | `String` | `en` |

packages/button/index.ts

@@ -22,6 +22,10 @@ VantComponent({
     size: {
       type: String,
       value: 'normal'
+    },
+    loadingSize: {
+      type: String,
+      value: '20px'
     }
   },
 

packages/button/index.wxml

@@ -3,7 +3,6 @@
 <button
   id="{{ id }}"
   class="custom-class {{ utils.bem('button', [type, size, { block, round, plain, square, loading, disabled, unclickable: disabled || loading }]) }}"
-
   open-type="{{ openType }}"
   hover-class="van-button--active hover-class"
   lang="{{ lang }}"
@@ -15,7 +14,6 @@
   show-message-card="{{ showMessageCard }}"
   app-parameter="{{ appParameter }}"
   aria-label="{{ ariaLabel }}"
-
   bindtap="onClick"
   bindgetuserinfo="bindGetUserInfo"
   bindcontact="bindContact"
@@ -27,7 +25,7 @@
   <block wx:if="{{ loading }}">
     <van-loading
       custom-class="loading-class"
-      size="{{ size === 'mini' ? '14px' : '20px' }}"
+      size="{{ loadingSize }}"
       color="{{ type === 'default' ? '#c9c9c9' : '' }}"
     />
     <view