update package.json for Node v12

packages/growi-plugin-attachment-refs/package.json

@@ -1,6 +1,6 @@
 {
   "name": "growi-plugin-attachment-refs",
-  "version": "1.0.5",
+  "version": "1.0.6",
   "description": "GROWI Plugin to add ref/refimg/refs/refsimg tags",
   "keywords": [
     "growi",
@@ -45,7 +45,7 @@
     "react-motion": "^0.5.2"
   },
   "engines": {
-    "node": ">=8.11.1 <11",
+    "node": ">=8.11.1 <13",
     "npm": ">=5.6.0 <7",
     "yarn": ">=1.5.1 <2"
   }