Describe the bug

I need to control the tab index ordering. So I added a tabindex attribute to b-form-checkbox, b-form-checkbox-group, b-form-radio and b-form-radio-group.

But I found the tabindex attribute showed on a enclosed div element instead of the input element. I hope that the tabindex attribute shows on the input element. And it's better to be ablet to set a tabindex property in options object of b-form-checkbox-group and b-form-radio-group.

Steps to reproduce the bug

1. Define b-form-checkbox, b-form-checkbox-group, b-form-radio and b-form-radio-group.
2. Add a tabindex attribute to the each component.

Expected behavior

A tabindex attribute must show on a input element instead of a enclosed div element for b-form-checkbox, b-form-checkbox-group, b-form-radio and b-form-radio-group.

Versions

Libraries:

• BootstrapVue: 2.0.0-rc.27
• Bootstrap: 4.3.1
• Vue: 2.6.10

Environment:

• Device: Windows Laptop
• OS; Windows
• Browser: Chrome
• Version: Windows 10

Demo link

https://codepen.io/hidekatsu-izuno/pen/aeZXRy

Additional context

Nothing