docs: clarify $inspect.trace docs

Author: benmccann

documentation/docs/02-runes/07-$inspect.md

@@ -52,7 +52,8 @@ This rune, added in 5.14, causes the surrounding function to be _traced_ in deve
 	import { doSomeWork } from './elsewhere';
 
 	$effect(() => {
-		+++$inspect.trace();+++
+		+++ // $inspect.trace must be the first statement of a function body
+		$inspect.trace();+++
 		doSomeWork();
 	});
 </script>