Remove warning from `yarn lint:js`

[erikphansen]

Running yarn lint:js gives the following output right now:

❯ yarn lint:js
yarn run v1.12.3
$ eslint --quiet --ext .js --ext .jsx .
Browserslist: caniuse-lite is outdated. Please run next command `yarn upgrade caniuse-lite browserslist`
✨  Done in 90.35s.

It would be great to remove this warning:

Browserslist: caniuse-lite is outdated. Please run next command `yarn upgrade caniuse-lite browserslist`

[rianfowler]

❯ yarn lint:js
yarn run v1.21.1
$ eslint --quiet --ext .js --ext .jsx .
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

also this warning

[jhonnyoddball]

Both warnings have been fixed.

• caniuse-lite
• core-js