[Feature]: nvm: only show node version if folder has package.json

[enjunear]

Expected behavior

The nvm plugin should only show the node version if the current folder has a package.json file.
Otherwise, don't show the node version.

Current behavior

Always shows the node version when the plugin is loaded.

Possible solution

I don't know, but there's a similar discussion here: romkatv/powerlevel10k#373

Context

It just takes up extra line space when it is not relevant. E.g., working on a python project, or working on ansible.

Notes

You guys are awesome. <3