[Docs] i18n docs add japanese (#37233)

docs/development/plugin/development-plugin-localization.asciidoc

@@ -13,6 +13,7 @@ You must add a `translations` directory at the root of your plugin. This directo
 .
 ├── translations
 │   ├── en.json
+│   ├── ja-JP.json
 │   └── zh-CN.json
 └── .i18nrc.json
 -----------
@@ -40,7 +41,8 @@ To use Kibana i18n tooling, create a `.i18nrc.json` file with the following conf
   "exclude": [
   ],
   "translations": [
-    "translations/zh-CN.json"
+    "translations/zh-CN.json",
+    "translations/ja-JP.json"
   ]
 }
 -----------

docs/settings/i18n-settings.asciidoc

@@ -13,5 +13,6 @@ Kibana currently supports the following locales:
 +
 - English - `en` (default)
 - Chinese - `zh-CN`
+- Japanese - `ja-JP`
 
 

docs/setup/settings.asciidoc

@@ -304,7 +304,7 @@ disable the License Management user interface.
 `xpack.rollup.enabled:`:: *Default: true* Set this value to false to disable the
 Rollup user interface.
 
-`i18n.locale`:: *Default: en* Set this value to change the Kibana interface language. Valid locales are: `en`, `zh-CN`.
+`i18n.locale`:: *Default: en* Set this value to change the Kibana interface language. Valid locales are: `en`, `zh-CN`, `ja-JP`.
 
 
 include::{docdir}/settings/apm-settings.asciidoc[]