message: [changelog] 2.0.8
diff: # Changelog
  +### [v2.0.8](https://github.com/youzan/vant/tree/v2.0.8)
  +`2019-07-16`
  +
  +**Improvements**
  +
  +- Sku: support custom placeholder [\#3864](https://github.com/youzan/vant/pull/3864)
  +- DropdownMenu: add icon option [\#3855](https://github.com/youzan/vant/pull/3855)
  +- DropdownMenu: optimize title ellipsis [\#3847](https://github.com/youzan/vant/pull/3847)
  +- ImagePreview: support double click zoom [\#3839](https://github.com/youzan/vant/pull/3839)
  +
  +**Bug Fixes**
  +
  +- fix Tab: click event param missing [\#3866](https://github.com/youzan/vant/pull/3866)
  +- fix List not work when body is the scrolling container [\#3844](https://github.com/youzan/vant/pull/3844)
  +- fix IndexBar incorrect active anchor in some cases [\#3832](https://github.com/youzan/vant/pull/3832)
  +
  +
  ### [v2.0.7](https://github.com/youzan/vant/tree/v2.0.7)
  `2019-07-11`
  