Update unist-util-is

[wooorm]

Hi! 👋

I was planning on updating this, but unist-util-is removed equality checks in favour of partial property checks (syntax-tree/unist-util-is#1, I remember we talked about that issue, maybe on Gitter?)

Anyway, this project uses equality checks a lot (in tests and examples at least). So what should we do?

a) overwrite partial checks with a type (e.g., remove(tree, {type: 'listItem'})) as an equality tests?
b) expect people to pass in equality checks themselves (e.g., remove(tree, n => n === someNode)).

[eush77]

I definitely remember the conversation, must not have foreseen the consequences for this project then.

I feel like option (a) would be confusing, and that option (b) is better in that it is more consistent with the rest of the ecosystem.

We can also drop array-of-nodes form (which is my invention): the only use I found is in an apparently deprecated project, so that should be no problem.