initial return type handling

examples/helloworld/src/lib.rs

@@ -11,6 +11,16 @@ fn hello_world() {
     printf("Hello world, Rust!");
 }
 
+#[ivory_export]
+fn add1(input: i64) -> i64 {
+    input + 1
+}
+
+#[ivory_export]
+fn format_hello(other: String) -> String {
+    format!("Hello {}", other)
+}
+
 ivory_module!({
     name: "demo",
     version: "0.0.1",