docs: update some examples of button and cell

src/cell/README.md

@@ -97,7 +97,7 @@ Vue.use(Cell).use(CellGroup);
 ### Vertical Center
 
 ```html
-<van-cell center title="Cell title" value="Multiple lines content, multiple lines content" />
+<van-cell center title="Cell title" value="Content" label="Description" />
 ```
 
 ## API

src/cell/README.zh-CN.md

@@ -104,10 +104,10 @@ Vue.use(Cell).use(CellGroup);
 
 ### 垂直居中
 
-通过`center`属性在多行文本时控制左侧标题垂直居中
+通过`center`属性可以让`Cell`的左右内容都垂直居中
 
 ```html
-<van-cell center title="单元格" value="多行内容多行内容多行内容多行内容" />
+<van-cell center title="单元格" value="内容" label="描述信息" />
 ```
 
 

src/cell/demo/index.vue

@@ -56,7 +56,7 @@
     </demo-block>
 
     <demo-block :title="$t('verticalCenter')">
-      <van-cell center :title="$t('cell')" :value="$t('multipleLinesContent')" />
+      <van-cell center :title="$t('cell')" :value="$t('content')" :label="$t('desc')" />
     </demo-block>
   </demo-section>
 </template>
@@ -76,8 +76,7 @@ export default {
       urlRoute: 'URL 跳转',
       vueRoute: '路由跳转',
       useSlots: '使用插槽',
-      verticalCenter: '垂直居中',
-      multipleLinesContent: '多行内容多行内容多行内容多行内容',
+      verticalCenter: '垂直居中'
     },
     'en-US': {
       cell: 'Cell title',
@@ -91,8 +90,7 @@ export default {
       urlRoute: 'URL',
       vueRoute: 'Vue Router',
       useSlots: 'Use Slots',
-      verticalCenter: 'Vertical center',
-      multipleLinesContent: 'Multiple lines content, multiple lines content'
+      verticalCenter: 'Vertical center'
     }
   }
 };

src/cell/test/__snapshots__/demo.spec.js.snap

@@ -100,8 +100,10 @@ exports[`renders demo correctly 1`] = `
   </div>
   <div>
     <div class="van-cell van-cell--center">
-      <div class="van-cell__title"><span>单元格</span></div>
-      <div class="van-cell__value"><span>多行内容多行内容多行内容多行内容</span></div>
+      <div class="van-cell__title"><span>单元格</span>
+        <div class="van-cell__label">描述信息</div>
+      </div>
+      <div class="van-cell__value"><span>内容</span></div>
     </div>
   </div>
 </div>