Support for Cuba (CU)

[damiansakwinski]

Can we add a support for Cuban postal codes? According to wikipedia the format is NNNNN (5 numbers), which seems to align with this list: https://www.directoriocubano.info/postales/

[barbieswimcrew]

@damiansakwinski you're free to create a pull request with your changes. please don't forget to add unit tests to improve the code coverage.

[damiansakwinski]

@barbieswimcrew #62