message: docs: add radio shape usage
diff: @@ -51,6 +51,15 @@ export default {
  </van-radio-group>
  ```
  +### Custom Shape
  +
  +```html
  +<van-radio-group v-model="radio">
  + <van-radio name="1" shape="square">Radio 1</van-radio>
  + <van-radio name="2" shape="square">Radio 2</van-radio>
  +</van-radio-group>
  +```
  +
  ### Custom Color
  ```html
  