Add the ability to apply a mask to input fields

[atanas-dev]

Initially proposed in https://github.com/htmlburger/carbon-fields/pull/167 by @elvishp2006 .

[dmhendricks]

(I am aware that I can do this manually with JS, but...) Yeah, this would be nice. I think the Mask Plugin provides an interesting model.

(Not suggesting that all features would need to be the same/supported - as I said, it's an interesting model)

[emohamed]

I've started implementing this feature in branch feature/masked-input

TODO:

• [x] validation based on the mask
• [x] test across supported browsers
  • [x] documentation