message: docs: add resources for checkbox pkg
diff: @@ -37,3 +37,8 @@ whether one or more options are selected.
  <Checkbox value="three">Three</Checkbox>
  </CheckboxGroup>
  ```
  +
  +### Resources
  +
  +- https://www.a11ymatters.com/pattern/checkbox/
  +- https://www.sarasoueidan.com/blog/inclusively-hiding-and-styling-checkboxes-and-radio-buttons/
  