Don't pull in all of core-js with core (#1601)

[wegry]

Reasons for making this change

Two versions of core-js currently exist in my app because @rjsf/core pulls in @babel/runtime currently. There are two direct imports of core-js that I've opted to pull in pure imports for.

For the rationale of why library code shouldn't include polyfills, this comment
w3ctag/polyfills#6 (comment) explains my rationale. This is a breaking change though, if downstream folks were depending on @babel/runtime being around.

If this is related to existing tickets, include links to them as well. #1601

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[wegry]

Looks like removing core-js from the lib build here might patch up #1464 (comment) as well?

[jimmycallin]

i would like to see this get merged. this would solve issues with webpack 5 that i'm seeing due to the babel/runtime-corejs2 package being included.

[epicfaace]

This is a breaking change though,

That seems ok, we can merge this and then release a v3.

[epicfaace]

@wegry , what happened? Do we no longer want this PR?

[wegry]

@epicfaace I think I accidentally force pushed to this branch trying to get Netlify to build in #2196, and GitHub marked this as closed. Let me see if I can't patch it back up.

[wegry]

Looks like GitHub won't allow me to reopen the PR on with this branch. I'll spin up a new PR that links to this one.