please add proxy (http/socks5)

please add proxy (http/socks5)

`./dnsproxy -l 127.0.0.1 -p 53 -z -u tls://dns.google -u https://dns.adguard.com/dns-query`

Changed to

`./dnsproxy -l 127.0.0.1 -p 53 -z -http http://user:pass@11.11.11.2:8080 -u tls://dns.google -u https://dns.adguard.com/dns-query`

`./dnsproxy -l 127.0.0.1 -p 53 -z -socks5 socks5://user:pass@11.11.11.2:1080 -u tls://dns.google -u https://dns.adguard.com/dns-query`

In China, it is not connected to `https://dns.google`, so you must use the proxy to access, please add support proxy to request access.

http://www.17ce.com/site/http/20190906_2e38c980d05211e9a6fa6ff274fada70:1.html