message: docs(DatePicker): fix basic usage
diff: @@ -21,7 +21,12 @@ app.use(DatePicker);
  ### Basic Usage
  ```html
  -<van-date-picker v-model="currentDate" title="Choose Date" />
  +<van-date-picker
  + v-model="currentDate"
  + title="Choose Date"
  + :min-date="minDate"
  + :max-date="maxDate"
  +/>
  ```
  ```js
  