ci: update node versions for cI - #732

I updated the branch protection to expect the 20.x check to pass instead of 12.x

Uhm, maybe we should add back the 12.x test? Otherwise I think it would be technically a breaking change to release a new version, WDYT?

We should also update the README for Node 20.x support…

Uhm, maybe we should add back the 12.x test? Otherwise I think it would be technically a breaking change to release a new version, WDYT?

Hmm... good point. I'll add 12.x back in.

[Breadcrumb: link to the debate on whether this sort of thing constitutes a breaking change.]

That said, our node support policy is "supported node releases + 1 prior version", right? So with 16.x slated for premature end-of-life on Monday, we should be able to drop support for 12 & 14 at our leisure.