add note on deprecation

Author: Rich-Harris

sites/svelte-5-preview/src/routes/docs/content/01-api/03-snippets.md

@@ -214,6 +214,12 @@ Any content inside the component tags that is _not_ a snippet declaration implic
 </table>
 ```
 
+## Snippets and slots
+
+In Svelte 4, content can be passed to components using [slots](https://svelte.dev/docs/special-elements#slot). Snippets are more powerful and flexible, and as such slots are deprecated in Svelte 5.
+
+They continue to work, however, and you can mix and match snippets and slots in your components.
+
 ## Typing snippets
 
 Right now, it's not possible to add types for snippets and their parameters. This is something we hope to address before we ship Svelte 5.