Add Korean translations

[steppi]

This PR adds Korean translations to the website. Thanks @miknai! Let me know if everything in the rendered output looks good to you.

I made a few changes on top of Crowdin's output; fixed some formatting in the markdown files for the case studies, made the language name in the drop down 한국어 (Korean) to match what we have for Japanese, and removed a duplicate line in the list of releases in news.md.

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