pack: set private attribute in package.json

package.json

@@ -6,6 +6,7 @@
   "author": "jooy2 <jooy2.contact@gmail.com>",
   "license": "MIT",
   "main": "dist/main/index.js",
+  "private": true,
   "repository": {
     "type": "git",
     "url": "https://github.com/jooy2/vutron.git"