Fix babel core-js warning

[nasdan]

Fix babel core-js warning

[LissetteIbnz]

@nasdan, you should explain this warning. I would like a post about that 👏😊

[nasdan]

@LissetteIbnz, it's this babel warning:

WARNING: We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.

You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:

  npm install --save core-js@2    npm install --save core-js@3
  yarn add core-js@2              yarn add core-js@3

It means that right now babel is assuming that we are using core-js@2 but it will be change in future, so it's required to feed corejs version in .babelrc file and we need to install same version in package.json to ensure that babel is using the right one. I don't know if it could be a post :)

[LissetteIbnz]

Yes, I know that. I mean what version. You have set core-js3. Saskia estaría tirándose de los pelos...