docs: display all less variables (#7604)

src/progress/README.md

@@ -69,3 +69,18 @@ Use [ref](https://vuejs.org/v2/api/#ref) to get Progress instance and call insta
 | Name | Description | Attribute | Return value |
 | --- | --- | --- | --- |
 | resize | Resize Progress when container element resized or visibility changed | - | - |
+
+### Less Variables
+
+How to use: [Custom Theme](#/en-US/theme).
+
+| Name                             | Default Value   | Description |
+| -------------------------------- | --------------- | ----------- |
+| @progress-height                 | `4px`           | -           |
+| @progress-color                  | `@blue`         | -           |
+| @progress-background-color       | `@gray-3`       | -           |
+| @progress-pivot-padding          | `0 5px`         | -           |
+| @progress-pivot-text-color       | `@white`        | -           |
+| @progress-pivot-font-size        | `@font-size-xs` | -           |
+| @progress-pivot-line-height      | `1.6`           | -           |
+| @progress-pivot-background-color | `@blue`         | -           |

src/progress/README.zh-CN.md

@@ -78,6 +78,21 @@ Vue.use(Progress);
 | ------ | -------------------------------------------- | ---- | ------ |
 | resize | 外层元素大小变化后，可以调用此方法来触发重绘 | -    | -      |
 
+### 样式变量
+
+组件提供了下列 Less 变量，可用于自定义样式，使用方法请参考[主题定制](#/zh-CN/theme)。
+
+| 名称                             | 默认值          | 描述 |
+| -------------------------------- | --------------- | ---- |
+| @progress-height                 | `4px`           | -    |
+| @progress-color                  | `@blue`         | -    |
+| @progress-background-color       | `@gray-3`       | -    |
+| @progress-pivot-padding          | `0 5px`         | -    |
+| @progress-pivot-text-color       | `@white`        | -    |
+| @progress-pivot-font-size        | `@font-size-xs` | -    |
+| @progress-pivot-line-height      | `1.6`           | -    |
+| @progress-pivot-background-color | `@blue`         | -    |
+
 ## 常见问题
 
 ### 组件从隐藏状态切换到显示状态时，渲染不正确？