Add build-local npm command (#5)

Author: kkajla12

package.json

@@ -10,6 +10,7 @@
   ],
   "scripts": {
     "build": "webpack --mode production --config webpack.config.js",
+    "build-local": "npm run build && npm pack",
     "prepare": "npm run build",
     "test": "echo \"Error: no test specified\" && exit 1"
   },