Move example to intro and example block

Author: ehuss

src/items/external-blocks.md

@@ -397,16 +397,17 @@ r[items.extern.attributes.link_name]
 r[items.extern.attributes.link_name.intro]
 The *`link_name` [attribute][attributes]* may be specified on declarations inside an `extern` block to indicate the symbol to import for the given function or static.
 
+> [!EXAMPLE]
+> ```rust
+> unsafe extern {
+>     #[link_name = "actual_symbol_name"]
+>     safe fn name_in_rust();
+> }
+> ```
+
 r[items.extern.attributes.link_name.syntax]
 It uses the [MetaNameValueStr] syntax to specify the name of the symbol.
 
-```rust
-unsafe extern {
-    #[link_name = "actual_symbol_name"]
-    safe fn name_in_rust();
-}
-```
-
 r[items.extern.attributes.link_name.exclusive]
 Using this attribute with the `link_ordinal` attribute will result in a compiler error.