Add CI job to validate localized strings files

[NickEntin]

This ensures we don't forget to update a strings file when adding new descriptions.

[kruegermj]

🚀

Does this confirm that for every localized string defined in a swift file there is a matching key in a strings file?

[NickEntin]

Does this confirm that for every localized string defined in a swift file there is a matching key in a strings file?

Yep, exactly! And also that there aren't duplicate keys.