chore: declare node engine requirements

[Abhijeet Prasad (AbhiPrasad)]

Make it clear that we support Node 20+ in the JS SDK

[Luca Forstner (lforst)]

This change gives me a feel of dread - sorry that it comes so late. Every time we did this in the past, even if we thought it should be fine, people ended up complaining.

I am wondering whether for now we should just document a minimum version requirement and only add the engine with the next major?

[Stephen Belanger (Qard)]

Regardless of potential user impact, I would generally always consider the change of a minimum installable version to be a major change. Is there any reason not to just do a major now or soon-ish? The change itself LGTM, just a question of when to ship it?

[Abhijeet Prasad (AbhiPrasad)]

I am wondering whether for now we should just document a minimum version requirement and only add the engine with the next major?

yeah I'm fine with doing that. I updated #1841