Support HTTP_PROXY env

[imba-tjd]

Is your feature request related to a problem? Please describe.
It's conventional to support HTTP_PROXY (and HTTPS_PROXY) environment variables to configure proxy for web requests. As I tested this CLI app doesn't support it when using py install.

[zooba]

Good idea, though it will use your default proxy settings already. Adding support to override those wouldn't necessarily be a bad thing, though.

[test9999tset-rgb]

A very good and necessary idea, for example I never activate the Windows proxy configuration, the browser and the rest of the applications I use have their own configuration for the proxy, almost all of them use the HTTP_PROXY and HTTPS_PROXY environment variables, so that the services and other applications of the OS (Windows) do not generate internet traffic. In fact pip and many other applications made and/or related to python use these variables to take the proxy configuration. I think it would be very good and logical to maintain this standard.