feat(phone-number): implemented phone number support

[wim07101993]

Connection with issue(s)

Resolve issue #33

Testing and Review Notes

All previous unit tests should pass. Added a new test for generating phone numbers.

[drager]

Thank you! Just some thoughts below

[firatcetiner]

PhoneNumber() cannot be used in 1.3.0. @drager When do you plan to publish a new version that includes this PR? In the meantime, I will have to fetch the package from git instead of pub.

[drager]

@firatcetiner Please try out 2.0.0-rc-1

[firatcetiner]

@drager Thanks. I guess I will stick with the old version because I can not switch to the Flutter beta since 2.0.0-rc-1 requires Dart SDK version to be >=2.12.0 and the current Flutter stable channel has 2.10.5.