Feat: add & fix translation for DurationField

Author: TGoddessana

rest_framework/locale/ko_KR/LC_MESSAGES/django.po

@@ -320,7 +320,7 @@ msgstr ""
 #: fields.py:1351
 #, python-brace-format
 msgid "The number of days must be between {min_days} and {max_days}."
-msgstr ""
+msgstr "일수는 {min_days} 이상 {max_days} 이하이어야 합니다."
 
 #: fields.py:1386 fields.py:1446
 #, python-brace-format