[Feature] Enable specifying semver ranges instead of a specific Node version

[sheerlox]

If no installed version (whether system (#31) or Nodelix) is available -> install the latest version satisfying the range.

If Nodelix is used by multiple libraries a project depends on, maximizing the supported Node version range from each library will make installation faster and take less disk space.

[sheerlox]

Oh, wait ... even better: enable specifying auto as a version, which would determine the most recent Node.js version to install in order be compatible with all packages engine spec 👀

I think this is a good idea because specifying a Node version in our config.exs is duplicating already existing information (library engine compatibility).

This would involve something like:

• detecting all packages (and their versions) from package.json files & mix nodelix.npm install calls
• fetching their respective package.json files from npm
• resolving the optimal Node version/range to use for compatibility.

Resolving to a range would still be preferable for the same reason this issue exists.

Given all of this is a bit operationally intensive, it would probably benefit from being a separate Mix task that updates the Node version/range in the config, and that could be run in CI for dependency update PRs (e.g. Renovate/Dependabot).

Note: just dropping random thoughts tbh 😆