Make global packages always available

A very nice feature would be to make global packages are always available, like with Volta.

Current behavior

1. Run npm install -g rimraf with a NodeJS managed by vfox
2. The rimraf command is available
3. Run vfox use to a different NodeJS version
4. The rimraf command isn't found anymore

Expected behavior

1. Run npm install -g rimraf with a NodeJS managed by vfox
2. The rimraf command is available
3. Run vfox use to a different NodeJS version
4. The `rimraf command is available and it is ran by the NodeJS version on which it was installed.

I guess it may need some major changes to vfox core but it could also benefit other platforms, like Bun, Deno and Python pip packages.

The issue describes npm global packages disappearing after vfox use switches Node.js versions, but names no files, tests, or entry points. Start by locating the vfox-nodejs handling for npm install -g and version switching; done would mean a globally installed command remains available and runs with the Node.js version where it was installed.