It looks like `.epochMilliseconds` should work as a Map/Set key/member in some situations, though you'll need to preserve the instant in the value in the Map ca

It looks like `.epochMilliseconds` should work as a Map/Set key/member in some situations, though you'll need to preserve the instant in the value in the Map case if you want to preserve the zonedata / do further operations on the Instant. For the Set case you could use a Map{v.epochMilliseconds:v} and preserve the Instant. Not great, but I think we all blame JS for this rather than Temporal. This could be made to work by the runtime but then polyfills would fail.