Checkbox - add error state

[daniele-zurico]

The Checkbox should have one property in case of error:

isError?: boolean;

if isError=true we should add some classes to the style property of the container, checkbox, and label. In particular:

dcx-checkbox-container--error
dcx-checkbox-checkbox--error
dcx-checkbox-label--error

please make sure you create:

• test
• storybook documentation
• storybook unstyled
• storybook classBased

[daniele-zurico]

closed by #585