Translation: korean

[xnousnow]

I'm native, I'd like to translate korean. I tryed but don't know how the translation works.

When translation is done, I'll open a PR. I'll appreciate if you accept me.

[rxhanson]

Sure, I'll accept a PR for it. Here is the file to modify: https://github.com/rxhanson/Rectangle/blob/master/Rectangle/ko.lproj/Main.strings