Add Japanese translation (#5641)

src-ui/src/app/services/settings.service.ts

@@ -131,6 +131,12 @@ const LANGUAGE_OPTIONS = [
     englishName: 'Italian',
     dateInputFormat: 'dd/mm/yyyy',
   },
+  {
+    code: 'ja-jp',
+    name: $localize`Japanese`,
+    englishName: 'Japanese',
+    dateInputFormat: 'yyyy/mm/dd',
+  },
   {
     code: 'lb-lu',
     name: $localize`Luxembourgish`,