title: set custom PATH for npm
body: <p>Is there a way that I can add a directory to the <strong>PATH</strong> of npm. I DON'T want to add this directory to the machine <strong>PATH</strong>, just the one npm uses when running scripts.
  I know that npm adds <code>node_modules/.bin</code> in addition to any pre-existing machine <strong>PATH</strong> (see <a href="https://docs.npmjs.com/cli/run-script" rel="nofollow noreferrer">here</a>)</p>
  
  <p>To give more detail on my specific case. I have a project with nested directories, each with its own <code>package.json</code>. When running a script on a sub-directory which depends on a parent binary, the binary won't be found because it's not on the local <code>node_modules/.bin</code> but inside a parent <code>node_modules/.bin</code>.
  I could specify the path to the binary inside the script but this is cumbersome and makes the scripts less readable.</p>
  
  <p>So, is there a way to tell npm to export <strong>PATH</strong> before running every script? It's already doing something like this to add the local <code>node_modules/.bin</code></p>