feat: add Japanese locale (#6274)

packages/vuetify/src/locale/index.ts

@@ -11,6 +11,7 @@ export { default as hr } from './hr'
 export { default as hu } from './hu'
 export { default as id } from './id'
 export { default as it } from './it'
+export { default as ja } from './ja'
 export { default as nl } from './nl'
 export { default as pl } from './pl'
 export { default as pt } from './pt'

packages/vuetify/src/locale/ja.ts

@@ -0,0 +1,14 @@
+export default {
+  dataIterator: {
+    rowsPerPageText: '1ページあたりの件数：',
+    rowsPerPageAll: 'すべて',
+    pageText: '{0}-{1} 件目 / {2}件',
+    noResultsText: '検索結果が見つかりません。',
+    nextPage: '次のページ',
+    prevPage: '前のページ'
+  },
+  dataTable: {
+    rowsPerPageText: '1ページあたりの行数：'
+  },
+  noDataText: 'データはありません。'
+}