feat: add metrics module for monitoring

Initialize the Metrics structure to receive and process ping statistics as part of the monitoring subsystem.

src/main.rs

@@ -3,6 +3,7 @@ extern crate core;
 mod baseliner;
 mod config;
 mod log;
+mod metrics;
 mod netlink;
 mod pinger;
 mod pinger_icmp;

src/metrics.rs

@@ -0,0 +1,6 @@
+pub struct Metrics {
+    pub config: Config,
+    pub stats_receiver: Receiver<PingReply>,
+}
+
+impl Metrics {}