docs: specify trailingSlash should be set in root layout (#10270)

Author: geoffrich

documentation/docs/25-build-and-deploy/50-adapter-static.md

@@ -38,7 +38,7 @@ export default {
 export const prerender = true;
 ```
 
-> You must ensure SvelteKit's [`trailingSlash`](page-options#trailingslash) option is set appropriately for your environment. If your host does not render `/a.html` upon receiving a request for `/a` then you will need to set `trailingSlash: 'always'` to create `/a/index.html` instead.
+> You must ensure SvelteKit's [`trailingSlash`](page-options#trailingslash) option is set appropriately for your environment. If your host does not render `/a.html` upon receiving a request for `/a` then you will need to set `trailingSlash: 'always'` in your root layout to create `/a/index.html` instead.
 
 ## Zero-config support