Set default proxy ports to spec

For HTTP "If the port is empty or not given, port 80 is assumed."
See: https://www.rfc-editor.org/rfc/rfc2616#section-3.2.2

For SOCKS "The SOCKS service is conventionally located on TCP port 1080."
See: https://datatracker.ietf.org/doc/html/rfc1928#section-3

src/proxy.rs

@@ -153,7 +153,10 @@ impl Proxy {
             server,
             user,
             password,
-            port: port.unwrap_or(8080),
+            port: port.unwrap_or_else(|| match proto {
+                Proto::HTTP => 80,
+                Proto::SOCKS4 | Proto::SOCKS4A | Proto::SOCKS5 => 1080,
+            }),
             proto,
         })
     }