Uses deprecated core-js version 2.6.11

Hi, testcafe looks really cool so I wanted to try it. As soon as I yarn added it though, I got these messages:

warning testcafe > babel-runtime > core-js@2.6.11: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.
warning testcafe > testcafe-legacy-api > babel-runtime > core-js@1.2.7: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.
warning testcafe > babel-core > babel-register > core-js@2.6.11: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.

I knew something would be broken and indeed my app no longer compiles. As soon as I install testcafe I start getting a bunch of errors like this:

ERROR in ./app/App.js
Module not found: Error: Can't resolve 'core-js/modules/es.array.concat' in '/Users/xxx/Sites/xxx/app'
 @ ./app/App.js 4:0-41
 @ ./app/main.js
 @ multi ./app/main.js

This is happening because testcafe requires core-js@2.6.11 that's no longer maintained and my app is setup to use the most up to date core-js@3.6.5.

I really wanted to use testcafe since it looks very nice. Hope this issue can be addressed soon.

Reproduce the dependency warnings with yarn add testcafe and inspect the dependency chain through babel-runtime, testcafe-legacy-api, and babel-core. Check the reported failure in app/App.js and app/main.js; done means TestCafe no longer forces incompatible core-js versions and the application compiles successfully.