feat: add rust link a

__ffi/rust_link_a/src/main.rs

@@ -0,0 +1,13 @@
+mod hello;
+
+use std::ffi::CString;
+use hello::print_line;
+
+fn main() {
+    let str = "Hello world!";
+    let c_str = CString::new(str).unwrap();
+
+    unsafe {
+        print_line(c_str.as_ptr());
+    }
+}