Add links to some core-js polyfills

[zloirock]

No description provided.

[Elchi3]

Hey @zloirock, thanks for your PR!
Did you see we started to collect thoughts on how MDN should deal with Polyfills? openwebdocs/project#27 What do you think about it?

[zloirock]

@Elchi3 I didn't see this thread, but I saw some related. I agree that MDN should not contain polyfills directly.

I already had problems because of incorrect / incomplete MDN polyfills some times, for example, zloirock/core-js#702. In addition, I see some links to incorrect / incomplete polyfills on MDN pages. To fix it at least somehow, I made this PR.

core-js is the most popular polyfill of JS standard library, used on most websites (even a naive detection shows ~59% on TOP 1000 websites) and contains proper polyfills.

I didn't remove polyfills code from MDN since I'm not sure that it's in the scope of this PR.

[sideshowbarker]

I’d be happy for this to get merged. Having polyfill links in the See Also section at the end of articles is about as unobtrusive as it could be made — I mean as far as the goal of moving away from having polyfill code within the articles themselves.

We’ve also in this issue tracker had feedback from developers saying they quite like being able to get to polyfill info from MDN articles — so this PR seems to do a pretty great job of serving that need.

Also, I think — given the visibility that core-js has — the core-js polyfills have been vetted much more carefully and thoroughly than anything else out there may have been (and continue to get vetted and fixed and needed) and so we can have high confidence that linking from MDN to them is pointing developers at a quality resource.

As far as the question of removing the polyfill code we still have within the articles themselves, it seems not necessary to block this PR on that being done — the removals can be done in a subsequent PR. (I think in fact that given the comprehensiveness/thoroughness of this PR, we could just now confidently remove all remaining polyfill code from any articles in the javascript tree which have them — without worrying that it’d result in any information loss for developers.)

[Rumyra]

I agree with @sideshowbarker - I think these resources add value. If no one disagrees I will go ahead and merge this 👍

[Elchi3]

Yes, I hope to continue the conversation on Polyfills but please merge this, @Rumyra 👍

[sideshowbarker]

Denis, thanks much, and congrats on landing your first docs change here — welcome aboard 🎉