add trivial examples

examples/helloworld/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "helloworld"
+version = "0.1.0"

examples/helloworld/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "helloworld"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

examples/helloworld/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}