Create Proxy Matcher util

[seanmonstar]

Create a type in hyper_util::client::proxy that can be configured with proxy matching rules. It should be easy to also construct one based of environment variables, or system proxies.

Note, this isn't a proxy Service. Just a type that when we ask "does this URL need a proxy", it can answer with the proxy's URL, type, auth, etc.

For prior art, there's a similar type used internally in reqwest.

[andrzejSulkowski]

I'd like to try this one. I might need some guidance though as this is my first PR on this repo. If you agree please assign it to me

[seanmonstar]

That's great! For what it's worth, I partially started porting over the type from reqwest, but got then paused while I planned out the larger project. I've submitted a draft PR with what I had so far: hyperium/hyper-util#171

[andrzejSulkowski]

Can I push on your draft PR or should I branch out and create a new PR for you to review @seanmonstar?