macros3 solution

solutions/21_macros/macros3.rs

@@ -1 +1,13 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Added the attribute `macro_use` attribute.
+#[macro_use]
+mod macros {
+    macro_rules! my_macro {
+        () => {
+            println!("Check out my macro!");
+        };
+    }
+}
+
+fn main() {
+    my_macro!();
+}