Scripts: Missing corejs version in Babel config

[swissspidy]

Describe the bug
I am trying to use @wordpress/scripts for unit tests. Still running into #13364, but there's also another issue when running wp-scripts test-unit-js:

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

Indeed, @wordpress/babel-preset-default uses useBuiltIns when running tests, but does not specify the corejs version:

gutenberg/packages/babel-preset-default/index.js

Lines 20 to 21 in 354c1ff

	if ( isTestEnv ) {
	opts.useBuiltIns = 'usage';

To reproduce
Steps to reproduce the behavior:

1. Install wp-scripts in your project.
2. Try to run some tests
3. Notice error

Expected behavior

The Babel config should add the corejs option in that scenario.