Removed node 16 from CI and added node 22 instead

[smallsaucepan]

Drop node 16 from CI (end of life was a year ago). Add node 22 instead.

[mfedderly]

This is technically a breaking change because we're dropping node16 official support, but I also think that's fine.

[smallsaucepan]

Thank you both for looking at this.

we're dropping node16 official support

@mfedderly gotcha. In the interests of tidying up, where do we define that? Can't see anything in the readme.

[mfedderly]

@smallsaucepan I don't think we define it anywhere, but in other projects I've seen that they make a major semver break when they drop an old node version from support even if nothing else changes. For Node support I think that "We support currently supported versions of Node" is a reasonable policy, with browser support that gets trickier because I kind of expect people using modules other than @turf/turf to be doing their own transpile/polyfilling, but I know not everyone is being careful of every package in node_modules, for instance.