Bind the `Proxy` type object of wreq.

[0x676e67]

The current default proxy is insufficient to support more complex proxy logic, such as sending custom request headers to HTTP/HTTPS proxies and implementing domain name/IP filtering logic. We need to bind a Proxy object to support these sophisticated proxy handling mechanisms.

[ruyrocha]

@0x676e67 I'd love to work on this

[0x676e67]

If you want to experiment, you can refer to this example for porting:
https://github.com/0x676e67/wreq-python/blob/main/src/proxy.rs