Add example implementation for server and client

examples/client.rs

@@ -0,0 +1,21 @@
+#[macro_use]
+extern crate log;
+use radius_rs::client::Client;
+use radius_rs::code::Code;
+use radius_rs::packet::Packet;
+use radius_rs::rfc2865;
+use std::net::SocketAddr;
+
+#[tokio::main]
+async fn main() {
+    env_logger::init();
+
+    let remote_addr: SocketAddr = "127.0.0.1:1812".parse().unwrap();
+
+    let mut req_packet = Packet::new(Code::AccessRequest, &b"secret".to_vec());
+    rfc2865::add_user_name(&mut req_packet, "admin");
+    rfc2865::add_user_password(&mut req_packet, b"p@ssw0rd").unwrap(); // TODO
+
+    let res = Client::send_packet(&remote_addr, &req_packet).await;
+    info!("response: {:?}", res);
+}