add trivial examples

examples/serde_test/src/main.rs

@@ -0,0 +1,13 @@
+use serde::Deserialize;
+
+#[derive(Deserialize)]
+struct HelloWorld {
+    who: String,
+}
+fn main() {
+    let json = r#"{
+        "who": "serde"
+    }"#;
+    let hw: HelloWorld = serde_json::from_str(json).unwrap();
+    println!("Hello, {}!", hw.who);
+}