npm warns about `--global` deprecation

[ProspectPyxis]

When this plugin is installing packages from .default-npm-packages, it uses the -g flag. However, in new versions of npm, this gives a deprecation warning:

npm WARN config global `--global`, `--local` are deprecated. Use `--location=global` instead.

Looking at the source of this plugin, this should be an easy fix - I'm more worried about whether swapping flags here would be a breaking change for older npm versions?

[augustobmoura]

This is a hard one, we still want to support older versions of npm, so I'm leaning towards keeping it until we have a true breakage in NPM's API. After that the way only would to do it would be to probably change the command conditionally, depending on the current version of npm