Drop Node 10 support

[MichaelDeBoey]

Because it's EOL.

[ph-fritsche]

Why would you consider this a breaking change?
There won't be changes in this library and I don't think we promised to support a specific Node version anywhere.
We just happen to test on all currently supported Node versions because it's a reasonable thing to do. (Didn't make a feature release when adding tests for Node16 either.) It's just noise for the library consumers.

[nickserv]

We promise to support Node 10 in package.json:

"engines": {
  "node": ">=10"
}

If I remember correctly, Yarn fails builds on engine mismatch by default. This is therefore a breaking change for Yarn users on Node 10, and also any npm users that manually enable engine-strict.

[ph-fritsche]

Would it be reasonable to remove the engines restriction and make this a fix instead of major ?
We don't rely on any of the Node APIs in this package. We even support test environments in the browser.

[nickserv]

Would it be reasonable to remove the engines restriction and make this a fix instead of major ?

I feel like that would imply we're still supporting Node 10, which we're not really, since we already disabled it within CI in #685. Semver minor releases are supposed to be fully back compatible, so not saying we will try to support Node 10 is a breaking change, even if Node 10 still works, IMO. If you want us to continue supporting Node 10 explicitly, we could revert these PRs, but that could still prevent users from upgrading DOM Testing Library and React Testing Library.

We don't rely on any of the Node APIs in this package. We even support test environments in the browser.

True, but the Node version still affects other things we depend on such as JavaScript syntax and other feature support. Most browsers update themselves automatically so I feel like this is less of an issue with supporting browsers anyway.

Overall I think it's still a good idea for us to use engines, since it helps users understand if they're using a supported Node version and it's already something we do with DOM Testing Library and React Testing Library.