Button appearance for checkboxes and radio buttons

[avernet]

The idea is to provide button-like styling for radio buttons and checkboxes. Bootstrap has offered this feature since version 2.3.2, though it suffers from poor color contrast. We may prefer to create our own custom CSS rather than using Bootstrap's, allowing us to maintain our current markup structure unchanged.

We might not need a separate value for the appearance attribute (so the XForms layer wouldn't be aware of this). Instead, we could use a class, such as class="fr-button", added in addition to the appearance="full". How can we select this in Form Builder for a specific control, for all controls on the page, or through a property?

https://getbootstrap.com/2.3.2/javascript.html#buttons
https://getbootstrap.com/docs/4.0/components/buttons/#checkbox-and-radio-buttons