Checkbox.Item: Make the underlying TouchableRipple more configurable

**Is your feature request related to a problem? Please describe.**
I've applied border radius to Checkbox.Item, and it seems to work as expected. However, when the item is `pressedIn`, the underlying touchable ripple doesn't respect the item's border radius.

**Describe the solution you'd like**
Expose an API to tweak the TouchableRipple through rippleStyle or containerStyle.

**Describe alternatives you've considered**
I've considered not using the Checkbox.Item and manually implementing the component with desired level of configuration. But it's a much bigger lift.

**Additional context**