Update core-js to version 3

[micksp]

Hi When I use this package, i get a deprecated warning on npm install: deprecated [email protected]: core-js@<3.3 is no longer maintained

Could you update to core-js version 3.16.0 (currently latest) please?

I tried doing a pull request but I can't get the package to install let alone build (enormous amout of errors, seems node related), so I can't try out my change in package.json.