Language cleanup / switcher and support for more languages

[JaneX8]

I've noticed Korean results when searching for which I created this issue #85 but I think there also should be a language switch option that lists all available languages.

I also think that the file structure should move most files to ./en/ to be more consistent with the ./kr/ and also to be prepared for other languages being added. Which adds a whole new issue, how to keep track of changes and keep the translated versions up-to-date with the English one, considering that the English one will always be the latest version.