Add Japanese translation (#5641)

src-ui/src/app/app.module.ts

@@ -295,6 +295,7 @@ import localeFi from '@angular/common/locales/fi'
 import localeFr from '@angular/common/locales/fr'
 import localeHu from '@angular/common/locales/hu'
 import localeIt from '@angular/common/locales/it'
+import localeJa from '@angular/common/locales/ja'
 import localeLb from '@angular/common/locales/lb'
 import localeNl from '@angular/common/locales/nl'
 import localeNo from '@angular/common/locales/no'
@@ -325,6 +326,7 @@ registerLocaleData(localeFi)
 registerLocaleData(localeFr)
 registerLocaleData(localeHu)
 registerLocaleData(localeIt)
+registerLocaleData(localeJa)
 registerLocaleData(localeLb)
 registerLocaleData(localeNl)
 registerLocaleData(localeNo)

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`,