adding guessing game

rust-book/chapter-1/guessing_game/src/main.rs

@@ -7,9 +7,13 @@ fn main() {
 
     let mut guess = String::new();
 
-    io::stdin().read_line(&mut guess)
+    io::stdin()
+        .read_line(&mut guess)
         .expect("Failed to read line");
 
-
     println!("You guessed: {}", guess);
 }
+
+fn test(arg: String) -> String {
+    unimplemented!()
+}