Support authentication with session.resolveProxy()

[chrmarti]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Problem Description

I'm using session.resolveProxy() to add proxy support to VS Code's extensions. That is currently missing support for authentication because session.resolveProxy() does not return credentials stored in the OS' proxy settings.

Proposed Solution

session.resolveProxy() should include credentials stored in the OS' proxy settings.

Alternatives Considered

Someone should write a Node module doing this. Getting it right across platforms might be the main challenge. Not sure if Chromium's implementation for reading proxy settings could be extracted to make it reusable as a Node module.