message: fix mobile nav style
diff: @click="isOpen = !isOpen">
  {{group.groupName}}
  </div>
  + <div class="mobile-nav-group__list-wrapper" :class="{ 'mobile-nav-group__list-wrapper--open': isOpen }">
  <ul class="mobile-nav-group__list" :class="{ 'mobile-nav-group__list--open': isOpen }">
  <template v-for="navItem in group.list">
  <li
  {{ navItem.title }}
  </p>
  </router-link>
  - <zan-icon name="arrow"></zan-icon>
  + <van-icon name="arrow"></van-icon>
  </li>
  </template>
  </ul>
  </div>
  + </div>
  </template>
  <script>
  @@ -86,7 +88,7 @@ export default {
  }
  }
  - .zan-icon-arrow {
  + .van-icon-arrow {
  position: absolute;
  font-size: 12px;
  line-height: 1;
  @@ -95,15 +97,24 @@ export default {
  }
  }
  - @e list {
  + @e list-wrapper {
  height: 0;
  - transition: height .5s ease-out;
  + overflow: hidden;
  @m open {
  height: auto;
  }
  }
  + @e list {
  + transform: translateY(-50%);
  + transition: transform .2s ease-out;
  +
  + @m open {
  + transform: translateY(0);
  + }
  + }
  +
  li {
  list-style: none;
  }
  