Added pom.xml to distribute the CSL locales via Maven

Hi folks!

I'm currently working on a project called 'citeproc-java' which is a small wrapper around citeproc-js with some additional stuff (such as bibtex conversion). Since I would like to publish citeproc-java via Maven it makes sense to also publish the locales there so they are directly available for Java applications. That's why I'm sending you this pull request.

Please also see my other pull request for more information:
https://github.com/citation-style-language/styles/pull/690

Cheers,
Michel