Derive clone for TradingEnvironment

[matteosantama]

I hope you don't mind me throwing some issues at you. If I collect enough of them and they start to become urgent I'll open a PR myself.

Another quality-of-life improvement would be to make TradingEnvironment Clone. Consider

fn run(env: TradingEnvironment) {
    let mut kalshi = Kalshi::new(env); // <- env is consumed here
    ...
    // so I can't use it later, like this
    if env == TradingEnvironment::Demo { 
        ....
    }
}

Currently, I have to manually clone it by adding

let env_clone = match &env {
    TradingEnvironment::DemoMode => TradingEnvironment::DemoMode,
    TradingEnvironment::LiveMarketMode => TradingEnvironment::LiveMarketMode,
};

[dpeachpeach]

Yep! Strong suggestion and should be a quick implementation, I'll work on this :)