feat(i18n): Add translation fields for de, en, ja, km, zhcn

- Update translation index to support Korean
  `application/src/translation/index.ts`
- Update translation indexes
  `application/src/translation/{de,en,ja,km,zhcn}/index.ts`
- Update dropdown menu item in dashboard header
  `application/src/components/dashboard/Header.tsx`

application/src/translations/en/common.ts

@@ -8,6 +8,7 @@ export const commonTranslations: CommonTranslations = {
   english: "Englisch",
   khmer: "ភាសាខ្មែរ",
   german: "Deutsch",
+  korean: "한국어",
   japanese: "日本語",
   simplifiedChinese: "简体中文",
   goodMorning: "Good morning",