feat(ActionSheet): add description prop (#4691)

src/action-sheet/README.md

@@ -16,11 +16,7 @@ Vue.use(ActionSheet);
 Use `actions` prop to set options of action-sheet. 
 
 ```html
-<van-action-sheet
-  v-model="show"
-  :actions="actions"
-  @select="onSelect"
-/>
+<van-action-sheet v-model="show" :actions="actions" @select="onSelect" />
 ```
 
 ```javascript
@@ -48,10 +44,7 @@ export default {
 ### Status
 
 ```html
-<van-action-sheet
-  v-model="show"
-  :actions="actions"
-/>
+<van-action-sheet v-model="show" :actions="actions" />
 ```
 
 ```javascript
@@ -76,11 +69,37 @@ export default {
   v-model="show"
   :actions="actions"
   cancel-text="Cancel"
-  @select="onSelect"
   @cancel="onCancel"
 />
 ```
 
+```js
+export default {
+  data() {
+    return {
+      show: false
+    };
+  },
+
+  methods: {
+    onCancel() {
+      this.show = false;
+      Toast('cancel');
+    }
+  }
+}
+```
+
+### Show Description
+
+```html
+<van-action-sheet
+  v-model="show"
+  :actions="actions"
+  description="Description"
+/>
+```
+
 ### ActionSheet with title
 
 ```html
@@ -98,6 +117,7 @@ export default {
 | actions | Options | *Action[]* | `[]` | - |
 | title | Title | *string* | - | - |
 | cancel-text | Text of cancel button | *string* | - | - |
+| description | Description above the options | *string* | - | 2.2.8 |
 | overlay | Whether to show overlay | *boolean* | `true` | - |
 | round | Whether to show round corner | *boolean* | `true` | 2.0.9 |
 | close-on-click-action | Whether to close when click action | *boolean* | `false` | - |