feat(Tag): add warning type (#4232)

src/tag/README.zh-CN.md

@@ -17,9 +17,10 @@ Vue.use(Tag);
 
 ```html
 <van-tag>标签</van-tag>
-<van-tag type="danger">标签</van-tag>
 <van-tag type="primary">标签</van-tag>
 <van-tag type="success">标签</van-tag>
+<van-tag type="danger">标签</van-tag>
+<van-tag type="warning">标签</van-tag>
 ```
 
 ### 空心样式
@@ -28,9 +29,10 @@ Vue.use(Tag);
 
 ```html
 <van-tag plain>标签</van-tag>
-<van-tag plain type="danger">标签</van-tag>
 <van-tag plain type="primary">标签</van-tag>
 <van-tag plain type="success">标签</van-tag>
+<van-tag plain type="danger">标签</van-tag>
+<van-tag plain type="warning">标签</van-tag>
 ```
 
 ### 圆角样式
@@ -39,9 +41,10 @@ Vue.use(Tag);
 
 ```html
 <van-tag round>标签</van-tag>
-<van-tag round type="danger">标签</van-tag>
 <van-tag round type="primary">标签</van-tag>
 <van-tag round type="success">标签</van-tag>
+<van-tag round type="danger">标签</van-tag>
+<van-tag round type="warning">标签</van-tag>
 ```
 
 ### 标记样式
@@ -50,9 +53,10 @@ Vue.use(Tag);
 
 ```html
 <van-tag mark>标签</van-tag>
-<van-tag mark type="danger">标签</van-tag>
 <van-tag mark type="primary">标签</van-tag>
 <van-tag mark type="success">标签</van-tag>
+<van-tag mark type="danger">标签</van-tag>
+<van-tag mark type="warning">标签</van-tag>
 ```
 
 ### 自定义颜色
@@ -68,9 +72,9 @@ Vue.use(Tag);
 ### 标签大小
 
 ```html
-<van-tag>标签</van-tag>
-<van-tag size="medium">标签</van-tag>
-<van-tag size="large">标签</van-tag>
+<van-tag type="danger">标签</van-tag>
+<van-tag type="danger" size="medium">标签</van-tag>
+<van-tag type="danger" size="large">标签</van-tag>
 ```
 
 ## API
@@ -79,7 +83,7 @@ Vue.use(Tag);
 
 | 参数 | 说明 | 类型 | 默认值 | 版本 |
 |------|------|------|------|------|
-| type | 类型，可选值为`primary` `success` `danger` | `string` | `default` | - |
+| type | 类型，可选值为`primary` `success` `danger` `warning` | `string` | `default` | - |
 | size | 大小, 可选值为`large` `medium` | `string` | - | - |
 | color | 标签颜色 | `string` | - | - |
 | plain | 是否为空心样式 | `boolean` | `false` | - |