Add enum example

enum_example/src/main.rs

@@ -0,0 +1,12 @@
+#[derive(Debug)]
+enum IpAddrKind {
+    V4(u8, u8, u8, u8),
+    V6(String),
+}
+
+fn main() {
+    let v4 = IpAddrKind::V4(127, 0, 0, 1);
+    let v6 = IpAddrKind::V6(String::from("::1"));
+
+    println!("Ipv4: {:#?}, Ipv6: {:#?}", v4, v6);
+}