Created by: wozzo
Implements #9739 allowing the proxy target to be set using environment variables and falling back to package.json if none exists.
Tested by running a project with the change applied.
- Ran with no proxy environment variable, but with proxy in package.json. Result: Used proxy from package.json
- Ran with proxy environment variable and package.json. Result: Used proxy from environment variable
- Ran with proxy environment variable and none in package.json. Result: Used proxy from environment variable