Add Phone Input Widget

[samends]

Enhancement

Currently there are a host of different specialized inputs for password, email, etc. It would be useful to add a PhoneInput widget to the repertoire.

[tomdye]

We looked at this but deemed phone number validation to be too complicated. Without baked in validation this would really just be an input with `type=’tel’` which didn’t seem like much value added. Initial issue can be found here: #791

[tomdye]

I think that we would only want to go ahead with this if we were to add a phone icon or similar to the leading / trailing section of this input. I had suggested this before for the email input but recall this being argued against. Perhaps we should discuss again?
Without this, we would not be adding much other than hardcoding the type as mentioned in the above comment.