add babel plugin

Author: swyx

package.json

@@ -27,6 +27,7 @@
     "not op_mini all"
   ],
   "devDependencies": {
+    "@babel/plugin-transform-object-assign": "^7.0.0",
     "babel-loader": "^8.0.4",
     "http-proxy-middleware": "^0.19.0",
     "netlify-lambda": "^1.1.0",