Add Japanese translations for Outliner

packages/node_modules/@node-red/editor-client/locales/en-US/editor.json

@@ -594,6 +594,7 @@
             "arrayItems": "__count__ items",
             "showTips":"You can open the tips from the settings panel",
             "outline": "Outline",
+            "empty": "empty",
             "globalConfig": "Global Configuration Nodes"
         },
         "help": {

packages/node_modules/@node-red/editor-client/locales/ja/editor.json

@@ -594,6 +594,7 @@
             "arrayItems": "__count__ 要素",
             "showTips": "設定からヒントを表示できます",
             "outline": "アウトライン",
+            "empty": "空",
             "globalConfig": "グローバル設定ノード"
         },
         "help": {

packages/node_modules/@node-red/editor-client/src/js/ui/tab-info-outliner.js

@@ -54,7 +54,7 @@ RED.sidebar.info.outliner = (function() {
     function getEmptyItem(id) {
         var item = {
             empty: true,
-            element: $('<div class="red-ui-info-outline-item red-ui-info-outline-item-empty">').text("empty")
+            element: $('<div class="red-ui-info-outline-item red-ui-info-outline-item-empty">').text(RED._("sidebar.info.empty")),
         }
         empties[id] = item;
         return item;