Add a -p for proxy flag

[davehouser1]

Would be great if I could send my requests to my Burp Suite proxy. Possible to add a -p flag for proxy?

Would look like this:

doh -k www.example.com https://10.10.10.10/dns-query -p 127.0.0.1:8080

[Hoasd]

+1

[bagder]

I'll happily receive a PR for that