Add optional character

[rodrigowbazevedo]

Add support for optional character, just need to put an ? in the pattern after the character you want to be optional.

With this feature it's possible to create patterns like this (11) 1?1111-1111, this pattern solve the problem we have in Brazil creating mask for phone numbers.

This PR is built on top of PR #39

[adiq]

Any plans for that feature? @insin

[digital-spectr]

Any plans for that feature?

[g0shed]

can we get this implemented or is this project dead?

[natanaelsimoes]

+1