[Vuejs]-How to use babel-polyfill in the following case?

try using the babel-transform runtime package: babel-plugin-transform-runtime

npm install --save-dev babel-plugin-transform-runtime

.bablerc located in the root of your project

{
  "presets": ["es2015", "stage-2"],
  "plugins": ["transform-runtime"]
}

you can now reset your entry param:

entry: {
  app: './src/main.js'
},