feat: Translate frontend/src/i18n/en.json in ko

90% of minimum 50% translated source file: 'frontend/src/i18n/en.json'
on 'ko'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

frontend/src/i18n/ko.json

@@ -24,7 +24,7 @@
     "ok": "확인",
     "permalink": "링크 얻기",
     "previous": "이전",
-    "preview": "Preview",
+    "preview": "미리보기",
     "publish": "게시",
     "rename": "이름 바꾸기",
     "replace": "대체",