Consider pinning the Node version to a specific number

[javagl]

Right now, the package.json specifies

"engines": {
  "node": ">=16.0.0"
},

There might be benefits in being more specific. The exact node version could be specified in an .nvmrc file, which could also be picked up by the CI script. I'm a bit on the fence here: On the one hand, it could avoid random build failures that are caused by random changes in some Node version. On the other hand, it should be possible to compile and run the tools on every Node version (>=16), and if there is an issue with one version, then this should be detected and fixed.

The implications for users/contributors also have to be investigated. (E.g. would pinning the version to 20.10 mean that someone couldn't even compile it without having this exact version?).