Support for SOCKS proxy

[Rush]

trafficstars

just discovered this project, and it’s pretty cool!

In the past, I’ve noticed that going through different SOCKS proxies and/or Cloudflare links can force vastly different routing, often unlocking extra speed—especially for long links, such as those from the US to Europe.

It would be really useful if this project supported SOCKS proxies as a way to add an additional link for improved performance and flexibility.

[surban]

This would be useful and probably straightforward to implement by adding a new transport using the tokio_socks crate.

However, at the moment I don't have a need for that myself and no time to implement it.

A PR would be welcome!