nit: bruh

exercises/21_macros/macros2.rs

@@ -0,0 +1,10 @@
+fn main() {
+    my_macro!();
+}
+
+// TODO: Fix the compiler error by moving the whole definition of this macro.
+macro_rules! my_macro {
+    () => {
+        println!("Check out my macro!");
+    };
+}