Add NN (Norwegian Nynorsk) locale

[snomos]

Adds a new locale - nn / Norwegian Nynorsk

Fixes # (issue)

Does not fix any issue.

Misc Checklist

• [ ] My change requires a documentation update on Sparkle's website repository
• [ ] My change requires changes to generate_appcast, generate_keys, or sign_update

My change should not need any change to anything, except for adding the new locale to the Xcode project.

Testing

I did not test anything, these are just strings. I don't have the knowledge or resources to test according to the suggested methods. I tried my best to not delete quotes or anything else that could mess up the string file syntax.

[zorgiepoo]

Thanks, it looks good but some Xcode project changes are needed too. I will include these in #2532 with your changes. I have tested them as well.