Added field `mix` to the options in radio-group/checkbox-group

Example:

```
{
block : 'radio-group',
mods : { theme : 'islands', size : 'm', type : 'button' },
name : 'radio-button',
options : [
{ val : 1, text : 'Футбол' },
{ val : 2, text : 'Баскетбол' },
{ val : 3, text : 'Гандбол' }
].map(item => { ...item, mix : { block : 'some-parent', elem : 'radio' } } )
}
```