Optional characters support

[DfKimera]

The library misses a very important feature of having optional characters in a mask definition.

For instance, brazillian phone numbers can be 8 or 9 digits long. So the mask (99) 9999-9999 is insufficient, and (99) 99999-9999 would look odd with a missing 9th digit.

Some other libraries handle this with the '?' character, as such: (99) 9999?9-9999.