Set `scheme` of proxy auth extension via protocol

[mdmintz]

Set scheme of proxy auth extension via protocol

Eg: If the proxy_string is "user:pass@https://host:port", then "https" becomes the scheme for the proxy auth extension. (Note that "http" is the default scheme if no protocol is provided with the proxy string.)

This becomes important if a proxy server is https-only.

[mdmintz]

This was resolved in 4.38.1 - https://github.com/seleniumbase/SeleniumBase/releases/tag/v4.38.1

[mdmintz]

There was a bug in 4.38.1. Users should upgrade directly to 4.38.2 - https://github.com/seleniumbase/SeleniumBase/releases/tag/v4.38.2