macros2 solution

solutions/21_macros/macros2.rs

@@ -1 +1,10 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Moved the macro definition to be before its call.
+macro_rules! my_macro {
+    () => {
+        println!("Check out my macro!");
+    };
+}
+
+fn main() {
+    my_macro!();
+}