Expose `_formatByMask`

[RodolfoSilva]

Could we expose the method from phone formatter _formatByMask as formatPhoneByMask. This will help when we need to format an unmasked number from the server.

https://github.com/caseyryan/flutter_multi_formatter/blob/master/lib/formatters/phone_input_formatter.dart#L175-L181

[caseyryan]

There is already a global method called formatAsPhoneNumber() won't it fit your goal?

[RodolfoSilva]

Sorry, thanks!