Add set_proxy_auth to client initialization if proxy auth is required

[unavailabl3]

This update is to add proxy authorization featrue to http client initialization. After it only need to add three environments:

HTTP_PROXY=http://1.2.3.4:5678
HTTP_PROXY_USER=username_for_proxy
HTTP_PROXY_PASSWORD=password_for_proxy

It made with the help of HTTPClient documentation httpclient#set_proxy_auth

[printercu]

Hi, and thank you for the contribution!

Is it possible to pass credentials like HTTP_PROXY=http://username_for_proxy:password_for_proxy@1.2.3.4:5678?

[unavailabl3]

Yes, it is possible
I think you can write about it in gem docs. It is very useful for countries where Telegram blocked