Add Tigrinya Language Support in GitLab

@gitlab-org/manage/import

I'm a Tigrinya speaker, and I'd like to contribute to GitLab's translation into Tigrinya (ti). Unfortunately, Tigrinya is not available in the Crowdin project.

Tigrinya is a Semitic language spoken in Eritrea and parts of Ethiopia, primarily using the Ge'ez script. Adding Tigrinya would benefit.