Add support for GSM Spanish language (Latin script) shift table

[Codesleuth]

See https://en.wikipedia.org/wiki/GSM_03.38#Spanish_language_.28Latin_script.29

This will hopefully pave the way for multi-lingual shift tables

[juliangut]

Do you have any interest in supporting shift tables? specially interested in Spanish and Portuguese

[Codesleuth]

@juliangut is this something you need? I'd be happy to review a PR if you can offer the feature

[juliangut]

Hi @Codesleuth , sorry for the delay but I've just created PR #16 to support not only spanish shift tables but turkish and portuguese as well

Let me know your thoughts