upgrade babel dependencies + config to support core-js@3

[mckernanin]

(likely a breaking change for core-js@2)

Fixes #119

[mckernanin]

Build is failing because core-js isn't installed/updated. Not sure if there's something special that needs to happen to update the peer dependency, I'm not super familiar with them.

[mckernanin]

Yep, adding it to the dependencies fixed the build. In master, core-js is in the lock file but not package.json. Is there a "right way" to do that, or just manually remove it from package.json?

[tizmagik]

I think having it as a peerDep is preferred in this case and then having it as a devDep would fix the build

[mckernanin]

Ah ok. Bumping the branch shortly.

[tizmagik]

Thanks @mckernanin I think I'll lump this with #124 so that we don't have 2 breaking releases back to back.

[mckernanin]

Sounds good, thanks!

[tizmagik]

Released as v7.0.0 🎉 Please holler (or open a new issue) if you see any problems.