Pass along required for custom checkboxes widgets

[fsteger]

Reasons for making this change

For custom checkboxes widget, required was not coming through. According to the documentation, the required prop should be passed through to custom widget components.
Reference - https://react-jsonschema-form.readthedocs.io/en/latest/advanced-customization/#custom-widget-components

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
  • I've run npm run cs-format on my branch to conform my code to prettier coding style
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[epicfaace]

Thanks! Looks good.