fix: locale ko-KR uses dayFormat 'D' instead of 'Do' (#786)

Author: jinhyeok15

src/locale/ko_KR.ts

@@ -16,7 +16,7 @@ const locale: Locale = {
   decadeSelect: '연대 선택',
   yearFormat: 'YYYY년',
   dateFormat: 'YYYY-MM-DD',
-  dayFormat: 'Do',
+  dayFormat: 'D',
   dateTimeFormat: 'YYYY-MM-DD HH:mm:ss',
   monthBeforeYear: false,
   previousMonth: '이전 달 (PageUp)',