chore: add npm version to engines field

[jviall]

since the package.json specifies a minimum node version of 18, it's probably a good idea to also specify the corresponding minimum npm version of 10, which is the version shipped with Node 18 (this will only trigger a warning if consumers for some reason are using an earlier version on npm along with node 18, so no need for a new major version).

With this change, it's also a good idea to delete and rebuild the package-lock.json again with npm v10, which upgrades the lockFileVersion from 2 to 3, the default for npm v10. This mostly just removes redundant info that version 3 optimizes out.

alternatively, you could just update the package-lock without specifying the npm version in engines

@davesnx I defer to you whether this should be a chore / fix / feat