Be clear that Node 18+ is required

[willeastcott]

• Explicitly declare in README that Node 18+ is required.
• Add a .nvmrc.
• Add an engines field to the package.json.

Fixes #6236

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[marklundin]

LGTM. Nice one!

[mvaligursky]

Could we also add this to .nvmrc to avoid to have to edit it locally?
registry=https://registry.npmjs.org/

Also, we should do the same for ./examples I think.

[willeastcott]

@mvaligursky That goes in .npmrc, not .nvmrc.

[kungfooman]

I used to build the engine on my old Ubuntu VM/server and it doesn't support node v18:

rollup/rollup#5497

There are hundreds of other people with the same issue: https://stackoverflow.com/questions/72921215/getting-glibc-2-28-not-found

The "solution" is "install v16"... software disintegrates quicker than you can fix it these days 😞