i18n(ko): Add Korean language support

[zephyranthes03]

Korean support

[jacobgkau]

@zephyranthes03 For future reference, it's best to avoid using underscores in branch names unless you're using it to build for a specific suite (e.g. _jammy). In this case, korean is not a valid suite, so the build server simply didn't build this for any suites. (The _nobuild string is not special, any non-matching string behaves the same as nobuild.)

I will push the same commit to another branch in order to make it build.

[jacobgkau]

The translation's showing up as expected in a user account set to Korean.