i18n: add Korean translations (#6963)

This pull request adds Korean translations.

I do want to add that while I do speak Korean _I am not a native
speaker_. I've done my best to provide translations as natural as
possible, but I'd love it if a native speaker could improve it before
merging.

src/os/i18n.zig

@@ -39,6 +39,7 @@ pub const locales = [_][:0]const u8{
     "ru_RU.UTF-8",
     "uk_UA.UTF-8",
     "pl_PL.UTF-8",
+    "ko_KR.UTF-8",
     "mk_MK.UTF-8",
     "tr_TR.UTF-8",
     "id_ID.UTF-8",