document $$props

site/content/tutorial/03-props/03-spread-props/text.md

@@ -6,4 +6,6 @@ If you have an object of properties, you can 'spread' them on to a component ins
 
 ```html
 <Info {...pkg}/>
-```
+```
+
+> Conversely, if you need to reference all the props that were passed into a component, including ones that weren't declared with `export`, you can do so by accessing `$$props` directly. It's not generally recommended, as it's difficult for Svelte to optimise, but it's useful in rare cases.