### Before submitting a pull request, please make sure the following is done:

1. Fork [the repository](https://github.com/youzan/vant) and create your branch from `dev`.
2. Follow the [contributing guide](./CONTRIBUTING.md) to setup your develop environment.
2. If you've added code that should be tested, add tests.
3. If you've changed APIs, update the documentation.
4. Ensure the test suite passes (`npm test`).

#### Title Format

[bugfix / new feature / improvement] ComponentName：content

Example：
* [bugfix] Button: color prop not work
* [new feature] Button: add color prop
* [improvement] Button: optimize performance