Move derive example into an example block

Author: ehuss

src/attributes/derive.md

@@ -4,29 +4,31 @@ r[attributes.derive]
 r[attributes.derive.intro]
 The *`derive` attribute* allows new [items] to be automatically generated for data structures.
 
+> [!EXAMPLE]
+> The following example will create an [`impl` item] for the [`PartialEq`] and [`Clone`] traits for `Foo`, and the type parameter `T` will be given the `PartialEq` or `Clone` constraints for the appropriate `impl`:
+>
+> ```rust
+> #[derive(PartialEq, Clone)]
+> struct Foo<T> {
+>     a: i32,
+>     b: T,
+> }
+> ```
+>
+> The generated `impl` for `PartialEq` is equivalent to
+>
+> ```rust
+> # struct Foo<T> { a: i32, b: T }
+> impl<T: PartialEq> PartialEq for Foo<T> {
+>     fn eq(&self, other: &Foo<T>) -> bool {
+>         self.a == other.a && self.b == other.b
+>     }
+> }
+> ```
+
 r[attributes.derive.syntax]
 It uses the [MetaListPaths] syntax to specify a list of traits to implement or paths to [derive macros] to process.
 
-For example, the following will create an [`impl` item] for the [`PartialEq`] and [`Clone`] traits for `Foo`, and the type parameter `T` will be given the `PartialEq` or `Clone` constraints for the appropriate `impl`:
-
-```rust
-#[derive(PartialEq, Clone)]
-struct Foo<T> {
-    a: i32,
-    b: T,
-}
-```
-
-The generated `impl` for `PartialEq` is equivalent to
-
-```rust
-# struct Foo<T> { a: i32, b: T }
-impl<T: PartialEq> PartialEq for Foo<T> {
-    fn eq(&self, other: &Foo<T>) -> bool {
-        self.a == other.a && self.b == other.b
-    }
-}
-```
 
 r[attributes.derive.proc-macro]
 You can implement `derive` for your own traits through [procedural macros].