feat(plugin-redirects): add Japanese translations (#15080)

### What?

Add Japanese translations for `plugin-redirects` and register the locale
in the translations map.

### Why?

Provide localized admin UI strings for Japanese users of the plugin.

### How?

`packages/plugin-redirects/src/translations/languages/ja.ts` and add
`ja` to `packages/plugin-redirects/src/translations/index.ts`.

Author: Robot-Inventor

packages/plugin-redirects/src/translations/index.ts

@@ -3,11 +3,13 @@ import type { GenericTranslationsObject, NestedKeysStripped } from '@payloadcms/
 import { en } from './languages/en.js'
 import { es } from './languages/es.js'
 import { fr } from './languages/fr.js'
+import { ja } from './languages/ja.js'
 
 export const translations = {
   en,
   es,
   fr,
+  ja,
 }
 
 export type RedirectsTranslations = GenericTranslationsObject

packages/plugin-redirects/src/translations/languages/ja.ts

@@ -0,0 +1,13 @@
+import type { GenericTranslationsObject } from '@payloadcms/translations'
+
+export const ja: GenericTranslationsObject = {
+  $schema: '../translation-schema.json',
+  'plugin-redirects': {
+    customUrl: 'カスタムURL',
+    documentToRedirect: 'リダイレクト先のドキュメント',
+    fromUrl: 'リダイレクト元URL',
+    internalLink: '内部リンク',
+    redirectType: 'リダイレクトの種類',
+    toUrlType: 'リダイレクト先URLの種類',
+  },
+}