Do not set NPM_CONFIG_PREFIX

[mpern]

Maybe it's just me, but I would prefer if the asdf-managed node.js does not change the default location for global node modules.

It took me a while to figure out why yarn and npm couldn't find the same global packages. It's because of the NPM_CONFIG_PREFIX injected by asdf-nodejs.

I propose to use the output of npm root -g instead of injecting non-standard defaults.

[mpern]

Related to #224, #22

[augustobmoura]

There's #228 for this exact problem. I'm kinda busy these last months, but I will try to make it spin again. My greatest concern is that removing the .bin prefix might break something unrelated, might be an unnecessary worry though

You (or anyone else interested) are free to try the branch and send any feedback