Update macros.md

docs/Rust/section7/macros.md

@@ -9,6 +9,8 @@ Macros in Rust is, in the most basic sense, "code that writes code", also known
 _metaprogramming_. By now, you have seen the `println!()` macro many times, and it illustrates how
 useful macros may be in everyday coding.
 
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 Another prime example that you have seen is the use of the `#[derive]` macro, which can implement
 traits on types automatically: