message: docs(ShareSheet): add custom icon demo
diff: @@ -14,7 +14,7 @@ Vue.use(ShareSheet);
  ### Basic Usage
  ```html
  -<van-cell @click="showShare = true" />
  +<van-cell title="Show ShareSheet" @click="showShare = true" />
  <van-share-sheet
  v-model="showShare"
  :options="options"
  @@ -52,8 +52,8 @@ export default {
  ```html
  <van-share-sheet
  v-model="showShare"
  - title="Share with friends"
  :options="options"
  + title="Share with friends"
  description="Description"
  />
  ```
  